I also stand my my initial response: 99%^ of these cases could've just been dealt with via content warnings 
Want to make a tweet explaining why you think gender = sex? Sure, do that - just tag it with (cw: gender critical) so people can ignore it if they want to.
Want to write a book about your experience as a pedophilie? Sure, do that - just tag it with (cw: pedophilia) so people can ignore it if they need to.
In so many of these cases, there's no good reason to prevent the information from existing. All the harms could be dealt with via a simple warning. Am I missing something or is it really not that complicated?
It's annoying, but I don't think that constitutes censorship - claiming something is off-topic or not engaging doesn't prevent the other person's argument from existing, and they're not stopping them from making a new topic where they can discuss the off-topic stuff.
For instance, calling out 'whataboutism' is essentially just claiming that something is off-topic. If, for instance you're talking about women's issues and someone comes in and are all like 'but men have it hard too', telling them to take that discussion elsewhere isn't saying they should shut up about men's issues or that they're not important - only that it's not what you're talking about right now, in this space.
For another example, I once discussed the merits of IP with @RobertBMarks and he ended the thread essentially saying I shouldn't have brought up my anti-IP ideas into that thread because it was off-topic. I was salty about it and was tempted to call him out on hypocrisy when he expressed an anti-self-censorship stance in this thread, but it would've been wrong of me to do so since he technically didn't ask me to self-censor - he just said I was 'hijacking' the thread we were discussing in and he probably wouldn't have minded if I made my own thread talking about my beliefs.
(Since there's plenty of salt in this thread already, figured it couldn't hurt to add my own two grams onto the pile :'D Besides, Robert has muted the thread already so it's not like he's gonna see this XD
And incidentally, as much as I've got a bone to pick with the guy, I can't help but notice that as soon as he brought up J.K Rowling^^, everyone focused on that part of his comment instead of the actual core of his argument:
I honestly want to know what pro self-censorship people's solution to this is, if they think some things should never be said. (Again, my solution is that everything should be allowed to be said - just some things should be tagged with a content warning.))
^ again, jokes are a difficult area, but stories and opinion pieces are 100% amenable to content warnings
^^ Just for the record, I'm not in camp 'Rowling did nothing wrong' - I'm in camp 'Rowling was wrong but allowing her to be wrong is a necessary consequence of a free society, and if she tags her incorrect speech, that already eliminates 99% of the negative consequences of her saying those wrong things'