Read other letters about this article
I admit I haven't read all 300+ letters so at the risk of repeating something, two things jump out at me.
The first is that leagally, threats aren't protected by the first amendment. You can criticize someone, even in an insulting way, but you can't threaten physical harm. I don't know the proper legal term, but threatening to slit someone's throat is a felony even without acting on the threat. So stop having a thick skin. Turn in the people with the violent comments. Maybe when they get a call from someone in law enforcement they'll get scared and stop.
The second thing is I don't understand why anyone lets unscreened comments onto a blog. I might see it differently if my own blog (http://www.ravensblog.net, pardon the plug) got more comments, but I decide if a comment goes in the blog. There's more legal responsibility for the content I'm sure, but even no threats go up. The controversies over the awful things posted on liberal blogs that were used to show how vicious the left is, and to tar those specific blogs, could have been avoided if the blogs in question had just screened comments instead of finding and removing them.