The left is a danger, but it is becoming laughable (please see DUFunnies for Thursday, South Park Katrina satire). The hard-core hatemongers of Democratic Undergraound are typical examples of hate gone mad on contemporary far-left liberal internal contradictions.
I only visited DU a couple of times and that has been awhile but my impression was it was just a bunch of loud mouthed kids trying to out radicalize each other. I consider them a gathering place for useful idiots.
Now Soros, the Clintons, and the old DNC operatives, Dean is just for contrast, are truly dangerous. They are shrewd, unprincipled and extremely ambitious. Most of the MSM are useful idiots as are the Hollywood bunch. They are a source of financing and free propaganda. Labor uniopns are other Communist operatives who supply lots of money and support.