He made them scrub with bleach water until he couldn't smell corpse smell anymore.

Yeah. I was telling a fib for comedic effect. Semmelweis is actually a lot more impressive, to me, because he was able to deduce that something important was going on and what the solution was, without having any idea what the mechanism might be, simply from observing and following the data. He didn't need to know the details to know it was a problem; he just trusted the evidence without needing to have a narrative built up in his head to attach it to.

Also, once he realized it was killing people, he wouldn't shut up about it until they literally had to kill him to make him stop. That puts him over the line from good scientist to hero, to me.

That is the TL;DR of Thomas Kuhn's "Structure of Scientific Revolutions." It is almost universal that when a new way of looking at the world comes along, very few people are persuaded to adopt it on an individual level. The consensus view generally stays the same until enough scientists who grew up with the old model die, that the ones remaining are outnumbered by new scientists who grew up with the new model.

It is bleakly comic, and there is surely some sort of productive lesson there, but I don't know what it is.

I’m hopeful this will be how we solve racism and intolerance… hopefully as enough people are brought up the right way, we will eventually move past the hatred in the world today.