The peak of their volcanic island smoking away, the primitive explains to their visitor from far away that the screams of terror and sobs he heard were simply of the virgin they’d had to sacrifice to the volcano god to keep the mountain from exploding. Things should be quieting down any moment now. They have nothing to worry about.
Their visitor doesn’t believe them, doesn’t believe in volcano gods or virgin sacrifices, finds human sacrifice, even animal sacrifice, a totally abhorrent practice, but politely refrains from saying so. Instead, he just nods and joins a few other unbelievers (all other visitors) in boats headed back out to sea.
He has no qualms about abandoning the barbaric virgin-sacrificing islanders to their likely fate while he gets safely away on his large swift yacht. He finds their willingness to deliberately murder fellow human beings evil and repugnant to the core. They’d only be dangerous to have around. He feels unclean now even having talked them so convivially as he did before he knew this about them.
A while later, with a thunderous droning sound and ash filling the sky around the island, a surviving islander pulls his canoe up beside one of the visitor boats and, seeing the same man he’d earlier explained about the virgin to, finds himself explaining again, this time a little embarrassed but still very firm in his faith: “She must have been lying about being a virgin.”
The visitor tries very hard not to roll his eyes. Whatever he says to the islander will make no impact on his faith. So he doesn’t. He doesn’t like the islander though. He personally doesn’t believe that human lives should be cruelly sacrificed to gods, regardless of whether or not they’re real. But what can he say?
A belief is a personal matter. It doesn’t have to make sense to anyone else. It is not even worth a real argument over as no two people believe exactly the same and it’s ridiculous even to expect it. Much as many a philosophy and religion pushes and tries to enforce Group Think, it never really works. Everyone interprets everything a little differently no matter what.
Saying someone will burn in a mythical unpleasant place called Hell for not believing what you do, will make no impact on someone who doesn’t believe in Hell other than making them dislike you a bit for wallowing in such heavy negativity, let alone wishing such things on you for not wallowing with them.
You’ll face even lower regard if you’re willing to kill for the sake of your god or religion. That’s just a fact of life. Nothing to be surprised about or claim unfair discrimination against you on. You give up human compassion in the name of anything and you automatically lose the regard of the greater world around you and your religion becomes a very foul looking evil thing indeed.