the worst trend for the left is the labelling. every argument that could be made has a catchphrase dismissal to go with (whataboutism, dog whistling), every person has a tag that you can demonise them with (alt right, nazi, bigot, straight white male) or stance on a singular issue that needs to be flagged up every time that person opens their mouth.
humans are wonky things that exist on analogues. for a progressive wing that can identify that there are a million different shades of sexuality and gender, they are awfully binary when it comes to morality or judge of character.
I used to think so, but now I think the most nefarious tactic is how vague and often repeated terms like "hurt" or "safety" are used. Directly related to this is accusing people are trying to enslave you or create a genocide, supported by playing a loose game of Six Degrees of Adolf Hilter with them (the former shows up more on tumblr, twitter, and campuses, but the latter is a GAF special). This strategy introduces a false sense of urgency and justifies really shitty behavior without a single implication of wrongdoing, because this person or book is making them "unsafe" or is "hurting" them. I find it quite unsettling seeing this in action, especially since it's almost always in the form of an angry mob. An explicit example of what I mean can be found in the Vulture article about a circle of authors playing judge, jury, and harasser for "hurtful" young adult novels on social media (unsurprisingly the dead about this died almost immediately and didn't break one page).
http://www.vulture.com/2017/08/the-toxic-drama-of-ya-twitter.html (recommended read)

It might be a bit of a stretch, but I think it is probably related to how many people in the google memo thread seem to think it was about calling women (and black people, even though race is not discussed at all) inferior and unintelligent when that's clearly not the case at all if you read it. It's so obvious most of the people in the that thread 1) did not read the memo 2) have not read much in the way of psychology or cognitive science regarding gender (or even know what "average" means). For whatever faults, you have to purposefully read it incorrectly to assume it was attack on human rights. All that was needed was for one to convince themselves or see someone else convince themselves they had a witch, so they could celebrate when they burned it.
Uncritical narrative building + mob mentality, and, to loop it back around, it goes from Salem to Orwell when words like "safety" are used to imply you have to defend yourself by any means necessary - against opinions.