I think flat earth falls into that category. However... the problem is there are also things that seem clearly like bullshit that we later find out not to be.

I think flat earth falls into that category. However... the problem is there are also things that seem clearly like bullshit that we later find out not to be. Have you ever been completely convinced about something that turned out to be entirely wrong? Almost certainly, probably more than a few times. It happens to all of us. And sometimes this happens on a societal scale with things like science and civil rights. Ideas not accepted at the time, attempted silence, but fortunately resisted censorship until history was able to bore them out.