A platform without ads or evil corpo ownership? Yeah, I'd scared too.
What I am getting at is that your insinuation that atheists spread child porn specifically is pretty baseless. If atheists are just as numerous on Reddit as a proportion of the userbase now as they were in the early days of reddit, and there's less child porn on there now - then they were obviously not the cause.
Moreover, I would guess that a majority of the Fediverse are atheists.