It doesn't have anything to do with diversity of opinion or lack thereof. If this article is correct, the issue is simply a blatant misrepresentation of what Stallman said.

I admit I haven't been following this news very well so far, so I'm doubtless missing some important facts. I'd heard Stallman was stepping down because of something he said about Minsky, but I have no idea what that was. If this is it, and this article is correct (edit: based on additional info here and elsewhere, it seems Stallman has a long history of questionable behaviour towards women that was also addressed in the initial article, so this new article is omitting quite a bit), then I'm baffled that he has to step down from anything. What he said, that the girl was coerced to appear willing, seems pretty clear to me, and presenting that as him saying that she was actually willing, sounds like a pretty clear and blatant lie to me. Seems worth criticising the organisations that spread that lie.

I'm generally in favour of fighting rape culture and child abuse with all that we've got, and Epstein is clearly pure evil. If Minsky has sex with an underage girl, it doesn't even matter whether she appeared willing or not; that's just wrong. In that sense, Stallman sticking up for his friend was probably not the greatest idea, but if he said she was coerced, and not actually willing, then it's wrong that he should lose his job for saying things he never said.

And yeah, sure, Stallman is a weirdo. Occasionally even a disgusting weirdo maybe (I remember a video where he seemed to pick something from his toes and put it in his mouth), and I recently read a description of events where he publicly embarrassed a woman for being present at a tech related event. (Edit: it seems he has a long history creepiness towards young women, including his students.) If you're gonna fire him, fire him for that, not for something he didn't even say in a private mailing list.

In general, I'm fine with weirdos. We need more of them, not less. Being a weirdo is no excuse to act like an asshole, but on its own it's no reason to ostracise someone.

But this issue? If the description from the article is correct, it seems based on a blatant lie.