When Eric Raymond, who is no longer officially involved in the Open Source Initiative (which he cofounded in 1998 or 1999 or so) addressed a forum of its members, OSI officials or forum officials banned him from the forum and invited anyone who felt traumatized by Eric's words or merely by his appearance on the forum to come forward.

What did he address that forum about, that caused this reaction? What was the claim against him?

I forget what he addressed the forum about. This happened about 7 y ago.

ESR writes a blog where he extolls libertarianism and is often skeptical of political progressivism.