Why do believers feel threatened by non believers?

In my own experience I’ve witnessed hate from religious people to those that don’t believe. I’ve also seen hate from non religious people to anyone that does believe. For some reason humans largely seem to be obsessed with others agreeing with their views whatever they may be. So to have people say plainly they don’t think the same way it can stir a frustration in some people. Some members of my family are religious. They’re good people & love me very much. They think I’ll burn in Hell not because I’ve done anything to hurt others but simply because that’s how it works in their beliefs. It crushes them to think I won’t be with them in their version of an afterlife. My cousin she is honestly the model of what I think a religious person ought to be for the most part. She truly practices what she preaches. She’s strong, smart, kind, generous, good natured. If more people religious or not behaved like her this world would be better for it. When it comes to others perceptions you can’t truly change them unless they’re open to it. We have to be ourselves & maybe many people will like us for who we are but not everyone will.