Being in favor of anonymity does not mean being in favor of personal attacks or handing over a license to use a vulgar term as a username. It’s about protecting people’s ability to speak freely without fear of becoming an outcast within the community for an unpopular opinion.

I can see your argument here, and I think that anonymity can be a powerful way to protect those who might be subject to retribution. I think whistleblowers' identities should be kept confidential, for example; I also think that incident reporting systems that allow anonymous reports of abusive behavior can be very beneficial.

My immediate concern about welcoming anonymous comments on a news blog (that it emboldens people to say cruel/bigoted things) is probably not realistic if the comments policy is enforced.

But that's where I get stuck: the idea that anonymity will allow powerful people to avoid the repercussions of bad behavior, rather than help less-powerful people speak truth to power. Common practice seems to favor the former. If your intent is to facilitate the latter, and it works, then I'm all for it.