I highly doubt you and I are socially or professionally connected and yet here we are.
Is that hard to disagree with? I didn’t even know atheism was a thing until I was on the Internet. No one in my community was an atheist and the media we were provided didn’t reference it much.
Personal anecdotes aside, we're mostly terrible at dealing with new ideas when they conflict with stuff we already know or is close to our identity. Remove the human element of the connection and we're even more likely to dismiss said conflicting ideas outright as stupid (I'll try link to that research). It's not hard to imagine how that might lead to strong yet poorly justified social division.