Antiseptic handwashing wasn't false. His theory for why it worked was; that theory was that "cadaveric particles" --- literally, corpse particles, and very specifically not a more general concept of microscopic infectious agents --- were to blame for ailments, and that chlorinated lime was the only way to get rid of them. Other doctors noted things like ailments in patients with no plausible contact with cadavers, to no avail: Semmelweis was insistent.

Semmelweis is, to me, an interesting story about how it's not all that useful to be right if you're unable to persuade, and Semmelweis' difficulties with persuasion have little to do with his adversaries bloody-mindedness and much to do with his.