They're right, it was unprofessional... but since the maintainer is not being paid this is not a professional project. It's a personal project. And this seems like a perfectly personal thing to do with something that's preventing happiness.
As an outsider I have to say that I think what the Rust community has technically achieved is remarkable. But on the social side it is not so bright, avid Rust users constantly spam forums of other programming languages with toxic comments. But this incident shows that the situation is even worse than expected, the Rust community even treats its own peers like sh..
For many people, their personal interest in open source is writing code for fun and showing it off. For others, it's making a product that people can rely on. The second one is my motivation; don't take that away from me.
If you are making products that people can rely on primarily because you enjoy it, you are literally an amatuer.
There are figurative connotations of quality and polish implicit with those terms, but I find those connotations unfortunate and in many cases unwarranted.
For instance, I don't pay a penny for HN but I can complain that these discussions sometimes become self-congratulatory prattle where angry people carrying a giant chip on their shoulder posit absurd, completely ridiculous notions and they're supported in their group delusion by like-minded parrots. You don't have to agree with my complaint, but nor do I need your or anyone else's permission to hold it.
Also, there are expectations for both sides of a professional interaction. My employer buys various fancy networking equipment for lots of money and we absolutely wouldn't expect an answer for that question.
If you create an organization on GitHub for a project that is meant to remain personal, this kinda sends a wrong signal.
Blaming some users for being rude and entitled, and then deleting an open source repo out of spite... it's a bit hard to feel sympathy for the guy here.
Sounds like there were intentions or plans to transform a one man project into something bigger. Some steps were made. Hence, a nice looking website, a github org, benchmarks etc. All those signals are intentions, the vision of the future self. They may or may not come true.
Nothing signaled an established business model or sustainable backing of any kind.
In this example it is held as a significant accomplishment on this individual's linkedin page. Which isn't surprising as professional credibility is a primary motivation driving a lot of open source involvement. We are seeking a different, less direct form of compensation.
So it's fair to say that acting like this is unprofessional.
That doesn't mean it isn't merited, or that they might have been frustrated or had good reason. But professionally they would have been much better served by other means: Simply announcing that they're retiring from the project and encouraging forking and the percolation of a new canonical version, etc.
Sure, if you want to spread the misery. That's still kind of a dick move, even if he's perfectly within his rights.