Earlier quoted context omitted.
I can't comment on most of the accusations, I have never met rms in person. But what really shocked me was that the authors of the anti rms letter label him as "transphobe", as a source for that claim they link to his GNU Kind Communications Guidelines [1], which to me spell the exact opposite. Why put such a claim in there? I find it really disturbing that so many people willingly accept that it's ok to mix legitima…
It's the bit about singular "they". RMS for some reason doesn't like singular "they", despite the fact that it predates singular "you" in common English usage. Singular "they" also happens to be, by far, the preferred pronoun of nonbinary people. By telling people not to use singular "they", RMS is harming, offending, and driving away nonbinary people from participation in GNU projects.
But now the footnote of the policy would allow you to call a trans woman "they" and never "her". That's not something transphobes (or anybody else) would ever do to a cis woman.