How is it insane to only welcome people to a community that act respectful towards other people? That seems like a really good way to build a solid community.
That's not the case with the Gleam community though. Unless you're willing to adopt their opinions / values / moral stance on certain issues, you won't be treated respectfully - you will be ostracized for having an unpopular opinion or view on a given issue.
It is a totally insane way to run a project, and it's quite obvious the Gleam community is run by persons who are unable to handle people with opinions that differ from their own.
It does sound like a great way to build an echo chamber.
I don't think Gleam has a problem if Kenneth Copeland is using their software, either. The problem arises when you mistreat community members in community spaces; I can't speak for DRH, but I'm reasonably sure if someone waltzed into SQLite's forum denigrating the devs and their religious beliefs, there wouldn't be much hesitation in removing that person from said forum.