The so-called "regressive" (I tend to call them New) Left didn't exist until they saw 25 years of the same tactics from Republicans actually working. I've been a liberal activist for almost 20 years, and a liberal for 30 in general, and I still remember the Vice President of the United States implying "liberal" was a curse word, on the campaign trail.
Of course, that's all an extension of old school McCarthyism, etc, etc. These tactics come from the right, and believe you me, all us old school Lefties are trying hard to stamp out the belief on our side of the aisle that rioting and being anti-free speech is in anyway progressive. Someone's got to be the grown up in the room.