(Question-the-Quo)
How did we get here?

Maybe I am young, but I had the impression that the Left in the 60s through...maybe the 90s?...encouraged rational thinking alongside active cooperation between movements for oppressed groups whilst acknowledging that these movements needn't be inclusive to ~everyone~.
So how did we get to the point where an entire generation of people associated as "leftists" (and who believes they are indeed the champions of the left it seems) are no-platforming people who have dissenting opinions (who are often left-leaning or marginalized themselves)? How did we get to the point where rapists, abusers, child predators, "incels", and racists are being welcomed with open arms into these movements within the Left (specifically the LGBT movements)?
Culturally, politically, and academically, how did we get here?

(pissedoff2ndwaver)
The left has always been misogynist. 1960s feminists broke off from the left because of their misogyny and started the second wave Women's Liberation Movement. See "Goodbye to All That" by Robin Morgan. http://faculty.atu.edu/cbrucker/Amst2003/Texts/Goodbye.pdf
The welcoming of rapists, abusers, child predators, "incels", etc pretty much follows from their misogyny, Not sure about racists.

(susannunes)
In large part true. However, the persecution of feminists on college campuses is a recent occurrence and a direct result of the poisonous pomo/queer theory that has polluted academia since the 1990s.

(susannunes)
They, at least the men, worship sexual liberation. Women are useful only for sexual access. It has always been such since the 1960s.
The no-platforming and silencing of feminists is a fairly recent occurrence. It is a direct result of the insane "queer theory"/postmodern drivel that has poisoned college campuses from the 1990s onward.

(lonewomanbiker)
At it's extreme, the left protects the rights of rapists, pedophiles, sex offenders, and trys to defend their actions.

(Mitya_Fyodorovich)
Culturally, we grew up in the MLK Day age. The age of MLK, Jackie Robinson, and Nelson Mandela as secular saints/racial santa clauses; conservative white people found the right formula to satisfy liberal white people and keep them from listening to black and leftist radical demands.
In the process we raised a generation of kids in the West to honor protests and "barrier breaking" but told them all the culture wars had been fought and barriers broken, because we don't want them going all the way to economic justice it has to be all about social acceptance. So, like Don Quixote, the millennial liberals go out in search of a Strom Thurmond or a Bull Connor to slay, and nevermind if it's a windmill.
Gay rights, especially gay marriage, played a fair part for a while, serving as a social wedge issue that didn't threaten Goldman profits. (This is not to say gay rights aren't legit, I'd never be in a position to argue that.) But once lgb rights were over, many were still filled with the social urge to support some "radical" social cause. Trans provides it.
Trans is perfect in this role, if it didn't exist it would be necessary to invent it. It frightens, or at least frightened for a while, the "squares." It's the fun kind of sexually liberating, for men anyway. It has virtually zero overlap with economic justice, other than posturing, and hence never threatens the C suite execs. It requires no lifestyle changes from the vast majority of adherents, the only non trans people from whom anything other than tolerance is demanded are school boards and lesbians. All anyone else has to do to feel righteous is "tolerate" a non contiguous minority group they'll probably never meet. And you can render yourself infallible and without sin by declaring you, too, are trans.