Because religion is absolutely about being closed minded. Are you open to other people's religions? No, of course not, that's against your religion. Are you open to other people's ideas? Of course not, it isn't in your bible and your preacher doesn't teach you anything about it so it must be wrong.

All a religion is is a shitload of people who decide they are only going to believe one thing and automatically say everyone else is wrong. Religion is the biggest load of shit ever.