I've noticed this too. I'm a grad student and am surrounded by liberals constantly. While many are nice folks, I've noticed that in general they are much more neurotic and have many more "issues" than the conservatives I know. I get the same impression when I lurk on DU - these people just aren't as stable as the general population. The question is, are they unbalanced because they are liberal, or are they liberal because they are unbalanced?
It's the classic 'Which came first, the chicken or the egg?' From my way of thinking, anybody who believes that Marxism is still the way to go after the abject failure of communism in the 20th Century has to be unbalanced.