I like that the community can give red rep. I was hesitant at first when we decided to do it, but I'm pleased with the result. It's a useful tool, even if only to vent your feelings about someone. Red rep, like all rep, is limited in how much you can give each day and how often you can rep the same person (you must rep x number of people before repping the same person again.) Therefore, if you have just one person "trolling" you with red rep, it shouldn't really make much difference overall. If you get a lot of red rep, maybe you earned it.

Now, instead of just walking a line to be sure you don't blatantly break forum rules and get an infraction, you also need to think about how people will react to your posts. I think it's brilliant. Plus, it's nice to be able to point out to someone their resemblance to the hind end of a mule, in a way they can't just delete and forget.