People always want to believe they are better than the rest of the world. If most of the world believes in God, that means they have to not believe in God just to prove how much smarter they are than those people.

If those people also happen to believe a lot of other things that are just common sense, they will reflexively also reject those things just so they aren't associated with those people.

Then they will engage in mental gymnastics to make it seem like the common sense thing they are disagreeing with doesn't actually mean what it means.

It's how you end up with the left saying women can have penises.