"[...]The idea is that good ideas should win adherents and bubble to the top while bad ideas sink to the bottom as they lose followers.[...]"

OK, but what if the good ideas sink to the bottom and the bad ideas bubble to the top, and people die? Because someone found the psychological triggers and the technical means to turn around the expected functionality of the good idea?

We all get the nice, philosophical, humanistic idea of free speech. But in the moment, it doesn't work so well. When something doesn't work so well, we have to fix it. So, what is the fix, in your opinion?