I think we need to own our feelings and accept them. "You can't heal what you won't feel." Stuffing feelings down is never a good idea.
It's perfectly normal and acceptable to have negative thoughts and feelings towards someone who has hurt us, how we act on those feelings is where we need to control ourselves
I never feel bad about my negative thoughts or feelings, but I get really, really mad with myself when I lose my dignity - for example when I completely lose my temper and scream and yell in an ugly way and then I have this thing where I throw coffee mugs at the wall... I always feel horrible when I do that, that to me is an unacceptable way of expressing an acceptable emotion.