(Mod: Apologies in advance for the length of this post; it is 100% Halacha discussion, and nothing else.)
Rav Bick ZTL, Rav Henkin ZTL and others all disagreed with Rav Moshe on many occasion, and they were entitled. But unless you are qualified to agree with one psak over another, and in the base sense of a prevailing halachic behavior in your family or community, you should follow whoever is the bigger posek (or poskim), and that often would mean Rav Moshe. However, that having been said, there is no such Halachic status as “Posek Hador”. Rav Moshe ZTL was great beyond great, but there is no reason to consider his psakim more authoratative than let’s say Rav Aharon Kotler or the Chazon Ish. There would be no reason, let’s say, to follow Rav Moshe’s shiurim for the Pesach seder than those of the Chazon Ish. In fact, Roshei Yeshiva and Poskim, such as Rav Hutner, Rav Eli Meyer Bloch of Telz, the Debreciner Rav, the Chelkas Yaakov and others, sided with the Satmar Rebbe over Rav Moshe regarding the obligatory size of a mechitzah in a shul, and/or the permissibility of artificial insemination, which were the two big disagreements that those Gedoim had in halachah. It was indeed Rav Hutner who approached the Satmar Rav asking him to write a refutation to Rav Moshe’s psak about the Mechitzos. You will not find the phrse “posek hador” anywhere in any meaningful way. The Tzitz Eliezer uses it all over the place in his titles, and, I believe, either the Teshuvos Maharshal writes it among the titles to the Ramah, or the Teshuvos Ramah about the Maharshal. But in any case, the title connotes no halachic status.
Unfortunately, many of those who use Rav Moshe’s psakim do so only when he is maikel. He permitted Cholov Yisroel (only b’shas hadchak – though they don’t pay attention to that part of the psak); he lowered the height of the Mechitzos — psakim such as these made life much easier for the Modern Orthodox, and even the out-of-town Orthodox communities. They believe they need Rav Moshe’s psakim to facilitate their mission as Modern Orthodox rabbis, or to be able to cater to the not-so-frum and do Kiruv. That is not a bad thing. A psak is a psak. However, when the same Rav Moshe prohibits Shabbos clocks (in most cases), or prohibits going to college, or paskens unequivocally that boys are prohibited m’doraisa to be “just friends” with girls, the same rabbonim with “Rav Moshe’s mechotzos” and cholov stam suddenly rely on “other poskim” (though in the case of boys being friends with girls, there are no poskim of anywhere near that stature who disagree with Rav Moshe). Part of it is due, too, to the fact that, at least in America, the other two personalities who were considered Gedolei Hador of that caliber were Rav Aharon Kotler and the Satmar Rav ZTL. Because of Rav Aharon’s stance on college and secularism in general, and the Satmar Rav’s stance on Zionism, there was no way in the world that those two Torah giants were going to be considered authoratative in what constituted the Orthodox community in America in those days. Instead, Rav Aharon was largley ignored, as it was predicted the followers of his hashkofo would become “mere tourist attractions” (thats a quote from Rav Y.B. Soloveichik in his “Five Addresses” about who he refers to as “seperatist Orthodox”. Rav Aharon was the leader of that Hashkafa), and the Satmar Rav was passed off as extreme by these people. In other words, it was “safe” for people to accept Rav Moshe and ONLY Rav Moshe because once you accept someone’s psakim in hilchos shabbos and kashrus, for example, you are forced to at least think about considering the fact that their stance against college or Zionism comes with as least as much authority. Of course, Rav Moshe Feinstein ZT”L deserved all the honor and respect that he received. He was a Gaon among Geonim and a Tzadik among Tzadikim, and one of the great Halachic authorities of our times. Thats not the issue. The issue is the fact that people pick and choose which Gaon-among-Geonim to follow when and because it is comfortable for them to do so.
The Gedolim in the days of the Shulchan Aruch and shortly thereafter have agreed to accept the psakim of the mechaber (and the Rema) as authoritative. The Shach writes that one cannot even claim “kim li” against a psak of the Shulchan Aruch. This is akin to accepting someone as your “Rebbi”, where you follow his psakim. This is the same thing that happened when, let’s say, Klal Yisroel decided that the period of Chazal has ended after the 7th generraiton of Amorayim (Mar Zutra, Mar bar Rav Ashi, etc), and nobody from here on in can add to the Gemora. There was no “halachah lmoshe misinai” that told us that the Gemora was sealed; it was the accepted reality told to us by our Gedolim. The same thign applies to accepting the Shulchan Aruch and Rema.
Because the Gezeirah was that a Jew has to supervise the milk, NOT that you have to have some kind of insurance that it is Kosher. Rav Moshe’s heter – however far one takes it – is to interpret the Gezeirah that any kind of insurance is sufficient to fulfill chazal’s gezeirah, which would make American milk cholov yisroel. But that itself is a matter of interpretation. If the Gezeirah was simply that you need a Jew supervising the milk, then even Rav Moshe would concede that even if you have reaosn to be comforatable that the milk is kosher, you still did not fulfill the gezeirah. In addition, even if you will accept Rav Moshe’s interpretation that the gezeirah is only that you need insurance not specifically Jewish supervision, who says that the laws are sufficient insurance that would satisfy chazal? If the penalty for violaitng the law is a fine, but the company will make more profit by violating the law, then how do we know that law is insurance? Very very often stores violate the Kosher Consumer laws. They put trief meat in the Kosher section etc, and they get fines that do nto deter them from being repeat offenders. Then there is the question as to who says the laws are being honestly enforced? As a certina godol said about the heter of the inspectors: “You give me two hundred dollars and I’ll give you four inspectors.” What halachic basis is thee to believe the inspectors are doign their jobs, being that Akum have no ne’emanus haalchicly?
Rav Moshe’s Teshuva (YD:5) says simply that the heter to eat cholov stam is “only b’shas hadchak”. Its pretty short and sweet. And this letter coincides with the letter to Rabbi Weinfeld of Monsey as well. Rav Moshe Feinstein ZT”L, in a letter to a Rabbi Weinfeld in Monsey, printed in “Hilchos Kashrus” by Rabbi B. Forst of Far Rockaway, explained what he meant with his “heter” for cholov stam. He says that even though there are rationales for saying that nowadays all dairy processed under government supervision has the status of cholov yisroel, it is still not proper to drink milk except under Jewish supervision, even if it is a bit more expensive or difficult to acquire. In a teshuva, someone – obvisouly not Rav Moshe – did put the titles on the teshuvos, and the title on this one says “Hidur l’hishtamesh b’cholov yisroel”, even though the Teshuva says it is indeed not merely a hidur but permissible b’shas hadchak. So the “yad zorim” did get in there, but its obvious they did not make up the Teshuva. In Rav Moshes subsequent Teshuvus, particularly the one in the last volume of IM, where he says his heter for Cholov Stam is only meant “bshas hadchak.” Thats a quote.
Rav Moshe’s heter is that it is possible that American milk is NOT cholov stam but cholov yisroel. if you hold that it is permitted, you don’t need a heter. CY is not a chumrah, it is a l’chatchilah, and there is a big difference. Everyone should be makpid on cholv yisroel halachicly, even according to Rav moshe – he says this clearly – unless there are dire circumstances. Rav Moshe sayus clearly in more than one place that unless there is a shas hadchak or some kind of dire need, it is not proper to drink cholov stam. Rav Moshe had his reasons for not making rules enforcing what he held to be correct. Perhaps he felt that not everyone was holding, yet, by doing the right thing. Who knows. Rav Moshe’s psak in his seforim that non Cholov Yisroel is not permitted except in strained circumstances. The last Teshuva, on this, in fact, is to a Yeshiva.
I probably would have interpreted Rav Moshe’s early Teshuvos – the statement “baal nefesh yachmir” is ambiguous enough to merit such an interpretation, for sure. But Rav Moshe himself, in two places – a letter that was first published NOT in Igros Moshe, but in other places (most notably Rabbi Binyonim Forst’s Pischei Halachah) and the latest Igros Moshe, printed not too long ago, Rav Moshe himslef interprets what he means – and he states clearly that he means you cannot drink Cholov Stam unless its a shas hadchak. In the last volume of Igros Moshe there is a teshuva on cholov yisroel where he explains what he means in previous teshuvos. Rav Moshe says – writes, rather, in a few places, that his heter to drink cholov stam is not meant to be used l’chatchilah, but rather ONLY B’SHAS HADCHAK!. Those are his words, not mine, and, in more detail, is reiterated by him in a second place.
The issue of cholov yisroel does not have naything to do with minhag. Whether your family does or doesnt use cholov yisroel, there is still a halachah in shulchan aruch that says you have to keep it. And Rav Moshe says that bshas hadchak, if you must have cholov stam, there is a heter. According to Rav Moshe, that heter (a) applies to all of klal yisroel equally, and (b) is halachic, not minhag-driven, (c) applies ONLY bshas hadchak – not a heter to buy Hershy bars, and (d) is still to be used only by non “baalei nefesh”, which he says should not rely on the heter. R’ Moshe Feinstein after hearing that he ate cholov stam – it sickened him such that he threw up.
As far as Utensils are concerned, the rule is, that when you cook something in a utensil, the utensil takes on the status of the item cooked in it. So if you coooked pork, the utensil takes on the status of pork, such that whatever you cook in it has the stats of pork; if you cook cholov akum in a pot, then whatever is cooked in that pot gets the status of cholov akum. Of course, the rules of Ben Yomo apply across the board as well – for the first 24 hours, the pot retains the status of the item cooked in it even bdoeved; afterwards, it is assur lchatchilah to cook in the pot, but bdieved the food may be eaten. That applies whether the food cooked in the pot was pork or cholov akum or whatever.