Your point is well taken. Is all the evidence out there that we quote perfect? It's probably not, and that's why things change. The thing that changes what we do is the evidence.
For years and years people thought that esophageal and duodenal ulcers were a weakening in the lining, but then they found out there is a bacterium that causes them, and now they're treated with antibiotics. It took evidence to change the previous evidence.