Um speak for yourself.
I think most of us atheists do think that but we're too polite to not say it. Besides, it won't change anything so there's no point.
Religions believe in a guy in the sky who promises to look after you after you have turned to dust after you do some arbitrary things during your time on earth. Most of their followers don't even actually do these things and are pretty bad people but still believe they're going to be looked after through some creative brain twisting. For this there is no evidence and no ability to even obtain it. The only thing they have is some old books.
I think the latter is more crazy in essence. Of course most flat earthers aren't actually interested in evidence and I think most of them just say they are in order to troll.
Also flat earthers are much less of a problem in the world because there's only a handful in them and most of them are in the US where they don't really stand out in terms of craziness considering the state that country is in. It's in a post-fact state anyway for most of its population.