No real point.
Most of these people are nuts, and what they say is of no real importance. Just showing how low it can go. And Alcaray is right--you can find some rotten stuff on conservative sites as well, particularly in the comment sections where the blogger doesn't have a lot of control.
As a rule of thumb, any site where the general public can post at will should not be held totally responsible for the content, at least on a short-term basis. And to be fair, that includes Democratic Underground's discussion boards.
Now, if you look at their front page, that's a different story.