This isn't a new problem.

Back in 2005, things were pretty nasty on the mailing lists. Today, I hardly see any personal insults. I don't see the nasty flame-wars that were so common at that time or even up to 2009. But things have changed, and the community has become much more accepting of differences. Maybe because most developers are now employed by corporations with HR departments. I only deal with the Linux kernel community, and can't express any opinions about other FLOSS projects, but as the kernel community seems to be the poster boy of insults, I would think that when it has become more tamed, so has the rest of the community.

I'm sure there may be an insult here or there, but when there's something like 700 emails a day, if there's a bad comment 0.005% of the time, that means you'll see one once a month. And the only times I do see people start to insult, is when the one being insulted totally ignores all the advice they received, and continue doing the same thing over and over, when finally, being 'nice' becomes a waste of time.

Another difference between Open Source projects and proprietary, is if you have a person who ignores all the advice from the lead, and continues doing things wrong, in proprietary, projects, that person can be disciplined in several ways. Either moved to another project, suspended, or even fired. It goes both ways. There's no HR for the project leads, but there's also nothing to stop someone communicating with them from consistently doing things wrong. In proprietary work you can say, "Do that again, and you're fired", it's much harder to do that in the open source community.

I don't condone insults to people. But when it comes to only using email for communication, insulting the code itself is usually much more efficient, and gets the point across much better.