Whether these perpetrators received the afterlife they expected, or whether such a thing exists (if it does, it certainly has nothing to do with any manmade religious doctrine), is largely irrelevant. The salient point is that they believe it exists, and that whatever they do is ultimately justified because, as the Bible so keenly reinforces, it’s okay to do objectively monstrous things (e.g. slaughtering an entire city’s worth of men, women and children) as long as you’re doing it in service of your god.

As long as people cling to these fairytales and fables as the inspired word of the creator of the universe, valuing their god more highly than other people, I don’t see how it can change. The solution would be to deconstruct and demystify the fairytales, revealing them for what they are, but when someone has bought into the delusion as hard as religious zealots tend to do, they’re much more likely to lash out than listen to reason.