While I understand and agree with the point you are making, I guess that is simply not the deciding issue for me when it comes to this topic.
For me, the main issue is one of responsibility. I'm definitely a believer in the idea "With freedom comes responsibility" -- if you want the freedom of speech, you should take responsibility for your speech. I believe that it can (but doesn't always) lead to speech that is more genuine and more thought through, if you know that you will be linked to what you say. I also believe that it promotes real discussions, whereas anonymous comments are thrown off and the threads abandoned more readily. Attaching your identity to your statements represents making a commitment, which (for me, at least) is something I respect.