I don't like contempt culture either but there's a balance to be made here - if you let everyone do everything and encourage them all as special snowflakes that can't create anything crappy, a community will also go to shit.
In this case it does sound like people initially were very nice and tried to give the author very polite suggestions on improvement, and it was only after the author being extremely dismissive[1], not admitting to his own flaws, not wanting to learn from others, and abusing his own power in shutting down valid discussion, that things turned nasty.
The fact that the author deleted many of the linked issues e.g. https://github.com/fafhrd91/actix-net/issues/83 really feels like he is playing the victim here and taking everyone for a ride, denying his own responsibility in all this drama that's unfolded.
Yes a community should be open and forgiving, but blindly forgiving someone who doesn't even admit their own mistakes, who doesn't even understand what they are being forgiven for, is naive and also will result in community destruction.
I also don't buy the "if you don't like it just don't use it" argument. If it's actively dangerous and you know this, and you know that other people don't know this, you do have a responsibility to (politely) inform others about it. Simplying "not using it" is plain negligence.
[1] "the patch is boring", LOL WTF I would never have even come up with something this insulting even when I wanted to actively piss someone off, kudos for imaginativity