I have a theory that Snape's grude with Harry is more over the fact he defited the man that was meant to bring him to greatness more-over the fact that James is Harry's father.
Is there... anything else? Might be nice to give us a little evidence to support it or something. It's a bit of a good idea I suppose, but I still think it's just as likely after what we've seen, that he loathes Harry because of James.
You're talking about what man? Lord Voldemort? He was the one supposed to bring Snape to glory? This ideea is a bit confusing... Or me too tired at this moment...
Voldemort was gonna bring nobody to glory. He's a loner and a user, his only concern about his associates is for their continued usefulness. If snape knew the first thing about Voldemort he'd know that much at least.
I'm not sure, but I think that's the sort of theory Tanuki has in mind, actually.
For Snape to be on his own side, watch Harry and Voldemort battle, and then try to destroy whatever remains.