[Havvy]

Bloodletting isn't witchcraft. It removes iron from the body such that virii and bacteria trying to reproduce would have problems. It makes the host environment more hostile to the invading species. It has a lot of negative side effects and wasn't very effective, but it did have an effect.

Of course, some people did bloodlet for reasons that didn't help, but without knowledge of bacteria, many were just trying their best with what limited knowledge they did have.