No human can prove the science of mandatory wearing of masks as it might prevent the spreading of the virus. It’s based upon non-scientific paranoia and the thrill of being a political tyrant.
And it has revealed far too many GOP state and local office-holders to be something very different than they pretend to be.
Nobody can prove anything. Science looks at evidence. Church choir: large room, no touching, lots of spacing, no masks, 80 - 90% infection spread. Beauty parlor, most had masks, talking (although not singing which is worse for spread), previously infected people, but no spread. You can look at evidence or you can ignore it. It's up to you.