Real evidence is objective. Real evidence is convincing no matter what belief you already have - assuming you're of a mind to go with what evidence implies.
"no matter"? no, that isn't true, it is possible for pretty smart mind to be blinded by belief in spite of pretty well any evidence. That's even true on the scientific side. New concepts sometimes are finally accepted as a consensus rather than with unanimity. Then final the few holdouts die off.
The ability to ignore evidence is pretty much all powerful if the belief is strong enough, I would say.