He's grown up in a world where he was told what was "right" and what was "wrong". And now he's finding out that things aren't what he had thought they were, and he's in too deep. He's a bit of a coward in the end, but he isn't "bad" necessarily.
The cast of Harry Potter discussing their favorite lines :) Oh Fred.... or was that George... If you don't remember that line its when he walks in on Harry and Ginny kissing in the seventh, part one :)