Yeah, until I read the comments, the context of that letter was not clear to me at all, as BDSM was only referred to in passing.
I only have a vague familiarity with the Gorean subculture. The modern subculture seems largely to be an extension of BDSM oriented role-play. The main negative I've heard is that Goreans sometimes take themselves way too seriously, ala a deep Star Wars or Star Trek nerd. I don't think I've ever heard them described as "abusive to women".
Even just adding "Gorean" within the letter would've helped me understand better. In literary circles, the books (after the first couple at least) do not have a great reputation, and they definitely have been criticized as sexist / misogynist (in addition to being simply bad pornographic writing). So it's easier to see how this sort of controversy can pop up.