One of my favorite sports blogs, The Wages of Win, recently examined its comment policy and cited a recent study by Dominique Brossard and Dietram A. Scheufele of the University of Wisconsin-Madison that was recently published online in The Journal of Computer-Mediated Communication.
The study had people read a fake blog post on nanotechnology (a subject chosen to minimize the likelihood of the readers having preconceived notions). Some participants were given the post with civil comments. Others were given the post with uncivil comments. Analysis focused on how civility affected risk perception of participants.
The study found that incivility polarized opinion. For example, someone with a positive view of nanotechnology would have their perception of potential risk decrease in the face of uncivil comments.
To me, this suggests that there is a trade-off. Pushing your beliefs in a manner that some may consider rude is likely to amplify the support of those who agree with you, at the cost of strengthening the beliefs of those who oppose you. For a site such as this, that may make it the correct strategy to be more rude on issues where there is consensus, while being calmer on issues that divide the community.