I don’t think he is evil either. Beside that scene he also had a scene towards the end of HBP where he told Harry that he was not a coward. And he couldn’t be one if he were spying on LV. I just think Snape had a hard time getting over the cool kids bullying him and he held a grudge. I also think he got in with LV and when things went too far, he got out. Sorta like Sirius’ brother.
I’m not sure bullying has anything to do with it...I speculate that Snape was just another guy totally captivated by Lily Evans... there has never been a bad thing said about her... I think we find out in the last book that Snape was devastated that he inadvertently caused her death. He doesn’t like Harry because he looks so much like James, but because he’s Lily’s son, he’s never hurt him either, he even stopped that curse in the last pages of HBP.
Less than 2 weeks till the final truth is known...
;D