I think the two phenomena are related. Were the left more "nitpicky about factchecking individual claims", it would be less vulnerable to such attacks. Reading Churchill reveals that he is not of the mainstream left. He is an irredentist ethnic nationalist, closer to Milosevic than anyone else I can name off the top of my head.
The left should have taken the lead in criticizing Churchill and his ilk. Instead, the left gave him kneejerk support, and is now paying the price in taking the blame for him.
I published in the midst of the right-wing firestorm only because my findings would not have been taken seriously before. I'm getting support I don't want from the right, and I'm getting uninformed ad hominem criticism from the left. Sometimes the world is upside down.
The left should never have fallen for the post-revolutionary chic that led to people like Churchill and Dohrn obtaining tenured positions. Now the left is getting beat up for owning these folks whose values would be abhorrent to most.