I'm against anything except self-censorship.

I don't think we should boot people out, but if someone were to do nothing but snipe at other members, advertize, or post messages to incite, (and I feel this is a very remote possibility) I could change my mind. If it's someone in our community who's just being a pain...well if this were real life, we'd just tell him to knock it off and ignore future inappropriate comments. I don't think any human is 100% bad, and we have an opportunity to encourage the good. If we don't do that, we lose.