“Something else I’ve seen – a bachur is home for Shabbos, and corrects his father at the Shabbos table in a very superior manner. Since when is it even permitted, much less simple derech eretz, to “correct” your father/mother openly in public”
Yes, I have seen this, too. The boys come home from 2 years of learning in E”Y, and all of a sudden they are re-arranging the kitchen and throwing out things that are in the pantry. I highly respect the Rov who instructed his talmidim NEVER to do this when they go home, that it is insulting to the kovod of their parents, and they have no right to upset the family dynamic.
In a home that is not Cholov Yisrael for example, the boy may ask his mother if she could get that for him along with the other household foods when she is shopping, but he cannot throw out her C”S or demand that she only use products under a hechsher that HE likes.
To correct a parent, is not only oveir their kovod, but also the mitzvah of “Ish Imo V’Aviv Tira-u.” There is a way to get one’s point across without sounding arrogant or smug. When that is not done in that way, then I cannot respect such a bochur.
Re: smoking – I can respect the Torah a bochur knows, and even respect him, if he is a mensch. But I cannot, will not, and do not, respect the choice he makes to inhale a well-known poison in his lungs on a regular basis, and then exhale it into the air that the rest of us are forced to breathe along with him.