If it turns out that the whole MIRI/LessWrong memeplex is massively confused, what would that look like?

Note that in the late 19th century, many leading intellectuals followed a scientific/rationalist/atheist/utopian philosophy, socialism, which later turned out to be a horrible way to arrange society. See my article on this. (And it's not good enough to say that we're really rational, scientific, altruist, utilitarian, etc, in contrast to those people -- they thought the same.)

So, how might we find that all these ideas are massively wrong?