"it's not that he's unable to understand, he's just unwilling to change his mind" do you mean unable to change his mind about the positions themselves, or unable to change his mind about when and how to air them? If he can at least agree that yes in retrospect that might have been an unkind thing to say in that context (even if he still thinks it's technically correct), but no he can't promise not to do it again because he's not very good at spotting insensitivity before it happens, then perhaps all he needs is a good secretary. He can say "post this to the list for me" and the secretary can look at it and go "hold on, this one doesn't look very good". And if he really is neurodivergent (which does not excuse his views, but might affect his ability to stop himself expressing them inappropriately), then he really should get a professional diagnosis: there might even be public funds that could help pay the secretary, just as people with other types of disability can sometimes have assistants; these would be available only with a proper diagnosis, so can we recommend he gets professionally tested?