Oh, I can totally see Snape seeing himself as The Good Son. I remember way back before OotP I described the way I thought Snape saw James on FAP and people thought it was obviously wrong--and then, of course, it was made canon in OotP. I just thought look, what has James *done* exactly? He just seems to have gotten killed. We've heard he defied the Dark Lord and blah blah blah but basically Snape seems to get the crap work with no credit. People really seem to just always see James in a good light--even McGonagall talks about him mistily, despite the fact that he was a great big rule breaker.

I think Snape represents something that is very true and most kids learn it pretty early: appearances count. A person with the right kind of charm can get away with stuff. Harry doesn't think of himself this way, but he benefits from it. He clings to his detentions with Snape and McGonagall as proof that he doesn't have any advantages that way, but he does. He's not James (he's not fun enough and never makes the effort to make anyone like him) but he benefits. Actually, he's a bit more James-like in HBP, especially in Slughorn's class.

With Snape it's hard to see where he gets any emotional stroking. The Slytherins seem to adore him. He must get it from there. (And of course fandom often tries to rewrite that so Snape can prefer Gryffindors too and see his own house the same way they do.)

The story of your friend really does seem to relate. That's the thing about Harry and the Dursleys--he's never trying to please them. Take that away completely and a lot of the tragedy is gone. Harry *never* wanted to please them. He didn't just later on develop a thick skin about it.