I agree with davem. I have never neg-repped anyone, perhaps because I know how I'd feel if someone neg-repped me. I may not agree with everything people say, but I don't see that as reason to mark someone down. If I really want to disagree, I'll remark in the thread, but generally I don't even bother with that. Seems better (and easier!) to just get along with everyone.
On the subject of some Downers not using their first languages, I feel compelled to say that I think everyone here communicates extremely well, no matter where they're from.