1) “The law goes according to the lenient opinion since it is a doubt of Rabbinical status (safek d’Rabbanan), . . . ”
If the known infestation levels of a particular food is greater than 50%, the food is considered muchzak b’tola’im and there is a chiyuv min ha’Torah to check. Such a case is NOT a Rabbinic prohibition but rather one of the Torah.
2) ” . . . for a person is not interested in eating the insect, but is compelled to eat it along with the food, against his will. .
. . ”
Since the particular food can generally easily be cleaned, removing all infestation, it is difficult to hear that anyone is forcing him to eat the bugs.
3) ” . . . Moreover, according to the majority of poskim, a tiny insect is batel b’shishim (nullified in sixty; that is, permissible so long as forbidden ingredients constitute no more than 1/60 of the whole) from the Torah, and it was only the Chachamim (Sages) who were stringent in declaring that a ‘briyah’ (a whole insect) is not batel (nullified) even in a thousand. . . ”
Something which ‘Only the Chachomim prohibited’ is nonetheless prohibited. And even the Kreisi who entertains the possibility that a berya is botul, is of the opinion it is so b’elef (1/1000, not 1/60) as suggested.
4) ” . . . Some poskim say that the Chachamim were stringent only in regards to an insect that has some importance, but if it is tiny and disgusting, even from rabbinical status, it is batel b’shishim. In addition, it’s also doubtful whether in actuality a tiny insect exists.”
What are the tiny insects “if they don’t even exist? An insect – for example a mite, which the nosei keilim on the Shulchan Aruch refer to as millbin or mill worms, is very visible and easily detected when they move, so there is little reason not to assur.
5) ” . . . Where can I find some sources to look through on this topic. It is quite surprising as most or all kashrus organizations make it seem as a Torah issur too eat vegetables that have not been checked for bugs.”
As explained above, any food with known or presumed infestation levels of above 50% is considered muchzak and they may not be eaten prior to checking. This obligation is a Torah obligation. From 10% to 50% (others say from as little as 5%) the obligation is to check remains, albeit of Rabbinical origin. Only levels below 10% (or 5%) are free from any obligation to check.