The first sentence of what he wrote is all you have to read really. It is like saying smoking menthol cigs prevents cancer. A straight, uncut, unstepped on lie.
The problem with progressives (which I am assuming you call leftists), as I see it is this:
They are the ones who insisted, way back in the day, that spanking your child is tantamount to barbarism.
They are the ones who, today, will tell you that you are a bigot because you disagree with gay marriage from a MORAL standpoint (supporting/opposing legislation against the group a different discussion).
They are the ones who insist a man who undergoes gender reassignment surgery is EXACTLY the same as a real live woman.
They are the ones who insist you call that transwoman a woman, or else, once again, you are deemed a bigot.
They are the ones who insist a 12 year old girl has the mental capacity to decide she is REALLY a boy. They are NOT old enough to legally fuck, but ARE old enough to decide they were shorted a dick and balls during conception.
They pushed gay marriage to the political forefront. I am CONVINCED this was a galvanizing factor that brought together otherwise disparate factions to support and elect tRump in 2016.
Progressives are OVERWHELMINGLY white, and therefore have the LEAST among us who oppose white supremacy to lose if and when things go south. They can just pretend to be neutral, or go along with the program.
I am not a fan of progressives. I supported Bernie at one point, but some of the things his cohorts stand for have contributed greatly to putting the nation in the position it currently is in.
You are "notreally" straight if you are that concerned with gay people. Literally all of your criticism of modern day progressives was just LGBT people.