Yeah, some sort of primer about being a safe space sounds like a good idea. I'm looking through the metafandom bookmark tags for prejudice, safe spaces, and privilege right now, but nothing has jumped out at me as being exactly what's needed. The closest I've found so far is List: Racism 101 which is, as the name suggests, a list of links about racism and privilege and being an ally, and I think a lot of the ideas contained in the linked posts can be applied to many or most -isms.