Welp... he hates JavaScript because of things he thinks he knows about JavaScript even though he's stating he knows nothing about JavaScript. Then he continues to ramble on about how browsers run JavaScript.
Someone so influential, and who sets the ethical standards for free software, should really do their homework.
I don't get why he didn't just say, "we won't support other languages because that's our vision for this software" and had to go into a bunch of unrelated bullshit. That's why no one listens to RMS's good ideas, because he talks about stupid, unrelated bullshit all the time. This talk was supposed to be about the future of Emacs, but the first part of it was dedicated to ranting about web JS?
Presumably people often suggest the misguided notion that Emacs should run JavaScript, and he wants to explain why this would be bad.