From the closing paragraph, I feel like he’s under the impression that Rust-advocating contributors are putting Rust’s interests (e.g. “legitimizing it” by getting it in the kernel) above the kernel itself.
If we're going to be serious about who is being toxic, it's definitely Linus in this thread. Guy makes first mistake (by a very broad interpretation of "mistake". Perhaps "misunderstanding"?). Linus goes nuclear. And while his reasoning is sound, his argumentation cycles between threats, bad-faith arguments, and just plain old yelling.
What some people don't understand is that the Linux kernel isn't 'led' in any meaningful sense. But I suppose some projects don't need actual leadership? I once was recommended a Metallica documentary, because "It's amusing to see what emotionally stunted 40-50 year olds who have never had anyone tell them 'No' since 18 will do." That's the Linus vibe -- somehow we've limped along to here. Seriously, read the rust/rust-lang issues/RFCs. Those people sound like grownups contrasted to this.
In my opinion, in the software world, there is a large number of people who are very convinced of their own correctness. When they do something wrong or are simply mistaken, a gentle correction doesn't work. Linus is probably used to dealing with these people. I'm not saying the person he was replying to was necessarily doing that, but after a while you have an automatic response.
The beauty and horror of OSS is that anyone can contribute. Having someone scream "WTF are you doing???" every once in a while isn't a bad thing. It's not nice to hear that being directed at you, but sometimes in life it is necessary.