The real trouble starts when regular people allow the "purity test" type people to have any sort of power or influence instead of laughing and ignoring them like we should. This can result in a destructive purity spiral, even over seemingly trivial issues.
https://unherd.com/2020/01/cast-out-how-knitting-fell-into-a...
I get that there are some 'purity test' type people out there, and they're annoying, but they're a small minority in most things.