I don't really have a dog in the race, but I think people should react this way to AI communication. They should be shunned and informed in no uncertain terms that they are not welcome to communicate any more.
He used AI as in he gave the AI the patch that regressed, asked the AI to "find the bug", and pasted that output.
This would be akin to walking up to the architect for a house, and saying "it's not my job to build buildings, but I tried to use this lego design to show you how to do your job. Look, the legos snap together, can't you do that with the house?"
Using AI to try and explain things to a subject matter expert, which you yourself do not understand, will come off like that, like you're second-guessing, belittling, and underestimating their expertise all at once.
Personally, the developers of both the LLVM and Mesa projects were far kinder and patient than I would have been, most OSS developers aren't just not paid to work on these projects, but are usually paid to work on other things. Taking up their time with this nonsense is very insulting to them, and the attitude that they owe the author anything at all is, as stated in the LLVM ticket, exactly what pushes many developers out of OSS development.
This might have been too petty to comment on, if it weren't for the irony that an arrogant human asserting that AIs are fallible made his own logical error or exaggeration in the same sentence. Was he designed to produce lies too?
Edit: I'm not really defending a layman using AI to produce patches, but the OSS developer's characterization is an overreach in the other direction. It's not a very useful heuristic either; at some point AI content is not going to be labeled or obvious, so it will have to be carefully evaluated for correctness and good-faith intention the same as human-generated content is.