In Yiddish, what are the differences in meaning among these words: ?

They're all nouns, they all denote the male organ and are used connotatively as derogatory terms for a man. None of them specifically evokes an element of volition vs, accident, but they do differ by degree. Schmuck is the most mildly insulting, putz is the worst.

Volition? Perhaps on the part of the speaker.

It is said that one may even call a friend a 'S...';

when he calls him a 'P***', he is more likely to be re-considering that friendship.

Edit:

One can no more act like a 'S***' or a 'P***' 'by accident' than he can direct such epithets by accident!