Neg repping someone because you disagree with their opinion is childish. I never neg rep anyone who doesn't do it to me first. I used to not retaliate, but then the same people kept doing it to all of my posts, so I realized they actually valued rep here for some reason, so i hit them where it hurt, and it stopped. I personally don't care about rep, but spreading negativity is not cool over opinions. I mean, if someone came in and called you a mfer, N-word, or something, I'd neg rep that. I never really see that though. But that's not an opinion...it's just useless insults of the most vulgar sort.
Notice in the OP I suggested NOT neg repping people. I even said why. It's futile to engage in such neg rep wars. Been there, done that. Can do it all damn day.