How is RMS an “ableist” or “transphobic?” I at least understand the claims of being a misogynist, but am not sure how there’s a case to even present him as ant

How is RMS an “ableist” or “transphobic?” I at least understand the claims of being a misogynist, but am not sure how there’s a case to even present him as anti-trans or whatever ablist means in this context. It’s so strange to see real orgs like CreativeCommons and Mozilla signing what seems like such a vapid letter.