Semmelweis's lies demonstrably (according to contemporary experts) hurt the reputation of the entire medical establishment of his day. Fortunately, back then, they had the recourse to put him in an insane asylum.
I wonder if a good modern analogy for Semmelweis would be if we did a study on crystal healing or Reiki, and the crystal healing/Reiki was found to vastly outperform placebo pills. (Actually something like this sort of did happen with parapsychology. The effect sizes were pretty small I believe, though.)
Obviously in hindsight, other docs still should've listened to Semmelweis. What I'm trying to get at here is that sussing out the truth can actually be a pretty tricky thing. Even if the docs had somewhat good reason to accuse Semmelweis of spreading medical misinfo, it was still a catastrophic mistake in retrospect.
I don't necessarily mean to indict the scientists of Semmelweis's day too much. I mean, they fucked up, to be sure. However it's understandable (somewhat) why they didn't listen to him.
But a society that allows those presently in power to censor information they consider to be false is a society that helps cement its present ways of doing things for eternity. I don't think that's a good thing.
A modern example of this might be the plaque theory of Alzheimer's disease. I don't know enough to know whether this is a fair description of the state of the science, but there is certainly a growing view that, a "cabal" of believers in this theory suppressed alternative views for a long time. It may end up being that the cabal is right! But it seems to me like there's enough uncertainty that a diversity of viewpoints should probably be heard.