You're missing 50% of the picture here. Anonymous, unmoderated discussion in an uneducated crowd is the worst of both worlds.
Obviously.
But anonymous, moderated discussion in a forum of disciplined and/or informed, educated users is better than the same discussion in a forum where all the identities of the participants are known, precisely for the reasons fat0wl outlined. You can look to any of the heavily moderated reddit communities for a great demonstration of this (AskScience, /r/sex, /r/fitness etc). Even cherry-picking the good parts of 4chan will make it blatantly obvious that anonymity, in a controlled setting, is a very good thing for the level of discourse.
The comment quality on many of these forums far surpass anything that you will see on politically correct Facebook, which is the opposite end of the spectrum: Most people, apart from a few loudmouths, will be exceedingly polite and well-behaved when all their friends are watching. And this leads to poor debate and boring discussion.
Even on Hacker News, I would refuse to contribute if I had to post with my full name. There are many reasons for this, but the biggest is simply that I do not wish future employers to be a Google search away from a detailed record of all my personal, political and professional opinions. This is simply a reflection on the fact that the reality of public discourse has changed in the world of search engines. Anonymity (pseudonymity) and moderation is the only way to resolve this problem.
In short, Google has the complete wrong idea. Which is actually quite shocking; Google should know better than anyone the realities of public discourse on the Internet.