The observation that the internet breeds impoliteness is an old one, and I don't intend to repeat it. I would just like to point out that there is something concrete you can do, which I'm trying to do more often.
Most people don't make death threats, but I feel pretty comfortable saying that most people's contribution to the Internet is a net negative for civility. We tend to post only to point out errors, to "correct" "mistakes", to explain to somebody in detail why they not only believe the wrong thing, but are stupid for believing it. Greivance Law 3 usually kicks in for at least two people, and cascading insults are a normal occurrence on the Internet.
Consider saying something nice. I mean, really nice, no strings attached. In this environment, I find it's best to include an indication that you are serious, because a simple "Nice." will often be interpreted as sarcasm. Why not? That interpretation is statistically likely to be correct. (My preferred tag is a simple "No sarcasm.")
In the small, this does nothing to affect death threats on the net. In the large, it can change the entire tone of discussion for a community for the better.
There are some obvious practical scale concerns (if 10,000 people read something not all 10,000 need to say thanks), but right now, we're well on the side of too few nice things said in general.
I'm not fishing; I don't need it. Working iRi is pretty stress-free, as you might guess from the comment count. Find somebody under attack that you agree with, or even just somebody who wrote something you found useful, and thank or support them.
Proximal trigger: kathy sierra, or, imminent death of the net predicted, but I've been thinking about this for a while now, well before this specific instance of trouble on the net.