Everyone should read through these even if they don't watch the video.
The slides cite various figures, such as " it takes 5 good interactions to make up for one bad one" and "assholes cause targets 80% lost time worrying". Does the video provide sources for these numbers that didn't make it into the slides?
http://blip.tv/tech-love-live/osb09-donnie-berkholz-assholes-are-killing-your-project-2464449
This is specifically about why it's important to get assholes out of open source projects, but it applies in general. It includes an analysis of the social cost of keeping people around who frequently make other people unhappy, and in particular a way to balance the social costs (distraction, people doing much less work or leaving, useful volunteers not joining, assholes recruiting other assholes, etc.) of assholes against the useful work some of them do.