Extreme leftists/regressive left may be rare in the general populace. They are not rare when it comes to the policy wonks, media, and famous activists. It seems that only the 2 extremes get a voice in the public sphere. The regressive left takes more time blaming and attacking their own county then terrorists and fundamentalists.
They have a huge influence on policy and weaken our freedoms. They also pave the way for the extreme right to take over. The regressive left is causing tremendous harm to our civilization.