And I would oppose measures that made anonymous posting to PM impossible. But you can still keep your real-life anonymity while logged in as a user to PM, no-one knows that user somerandoname is the same RL person as someotherrandomname (and it can be made impossible to trace somerandomname to a real person as well). Or you can post as AM with the slight drawback that your IP address is known and your posting can be traced back to your RL person by a determined entity(this is true today as well). As I said, I don't think that the inconvenience of creating a separate user is too great, given the benefits of such a measure.

Also, while I agree with your statement in principle I'm not sure it is perfectly valid with regard to PM. It's not like somebody is going to come and kneecap you for saying something unpopular. The worst that can happen is that you lose some XP which you can regain with a few thoughtful posts. And, for that matter, even if your view is unpopular I don't think you'll be downvoted overmuch if the view is presented in a rational and non-offensive manner.