I don't know why I'm always surprised when people respond to my posts on controversial subjects with personal attacks and venom. It's not unique to the blogosphere, of course; I deal with this in academic politics all the time, as well.
There are plenty of people online whose ideas I disagree with, or whose writing makes me angry. But in general, I try to separate out my responses to their ideas from my responses to them as people--particularly if they're people with whom I've had little or no personal interaction.
I'm fine with someone coming onto my site and saying "I think that's a terrible idea," particularly if they say why they think that. And I've found that most interesting discussions start not with "That's stupid!" (or worse, "You're an asshole!") but rather with "Well, here's why I disagree." Ad hominem attacks do little to set the tone for a debate.
Don't like what I say? Then debate the ideas. Think what I say is rendered worthless by my very existence? Then stop reading. But don't poison my comments with venomous, hurtful remarks. From now on, personal attacks on this site will be deleted without comment. Repeat offenders will be banned from the site.