as always 'magick has no colour, only intent'.
it really comes down to your set of morals if it's right or wrong. if you use 'black magick' when all else failed and you're out of options, then it would be fine karmically speaking. if someone knocked you down while running to class so you hex them, then you'll feel some negative karma your way. with any spell you should meditate on it, figure out if a spell is needed and the one you've chosen is the right one before you cast.