It is, I believe, because of the way the peer review system is employed.  Some people tacitly approve of his wanton attacks, and allow his statements to stand.  I will give him credit for attacking overtly rather than covertly (for the most part)....

I know CC is hoping this "mute" function will help - but it won't, in my opinion.  Those that employ it will only do so because they do not want to admit there are arguments against their opinions or those that disagree with them.  I don't think it is a good idea at all - stifling honest disagreement never is.  In my opinion, it is the peer review system that needs to be revamped and overseen rather than adding a "mute" function.....