"Extremists"
Oh, please.
Stop drinking the GOP Kool-Aid (I'm not suggesting you are necessarily a GOP-supporter, just that you're drinking their Kool-Aid). America doesn't have Extremists on the left any more.
If one of the Weathermen come out of retirement, get back to me.
Meanwhile, the most extreme that any Democrats get is 'wanting what has already been shown to work in every other first world economy'.