What a harebrained comment.

...Sorry, it felt like such a waste not to say it! The puns!

But, language Nazi? Don't you think that's a bit much? And it must be useful for everyone? Why? I also think it hinders growth, but it's their project. It's well within their right to choose whether they put in the effort to support a platform or not, regardless of the reasoning and how much effort it'd actually take.

They don't even seem to be against the idea, they just don't care enough to be the ones to do it:

According to DeVault, while there's currently no plan to support non-free platforms like macOS or Windows, a third-party implementation or fork could try to make that work. The Register

Even Emacs is available on windows, you say? I think some context is needed, here. See what GNU has to say about the availability of Emacs on proprietary systems:

However, GNU Emacs includes support for some other systems that volunteers choose to support.

Emphasis mine.

To improve the use of proprietary systems is a misguided goal. Our aim, rather, is to eliminate them. We include support for some proprietary systems in GNU Emacs in the hope that running Emacs on them will give users a taste of freedom and thus lead them to free themselves.

Taken from the official download and install page.