I lost all my friends when I voiced my gender critical views. Literally all of my friends dumped me and no longer speak to me because I'm just a stupid terf in their eyes. You are not alone.
I also lost one of my oldest friends because she was trans, FTM, I merely told her I'm a radical feminist and then she told me we could no longer be friends.
Twelve years of friendship negated at the drop of a hat. They really are a dangerous cult. I'm sorry your friend has been indoctrinated, but I'm afraid there's little to nothing you can do to change this. Take it from me, an experienced terf, he's already found his people and drank the Kool-Aid. It's too late. They can't agree to disagree, they won't hear out our opinions, and they wish death upon us. It's a lost cause.
I think it is having to do with autism. They can't comprehend someone not following societal "rules." They can't deal with masculine women or feminine men, because they don't fit any sort of societally acceptable roles. They also need to dictate all the changes in their bodies with cameras. I'm sorry for your loss.