That's taking the concept to an absurd extreme. Totalitarian belief systems that can't coexist with others can't be tolerated, yes, but it's nothing inherent in

That's taking the concept to an absurd extreme. Totalitarian belief systems that can't coexist with others can't be tolerated, yes, but it's nothing inherent in christianity - yet different Christian denominations spent decades killing each other in the Thirty Years' War. It's more of a character trait. Same personality type that was happy to kill all 'papists' would be a fanatic nazi in 30s' Germany and an eager killer for Pol Pot. People like that are always going to exist, what happens depends on the reactions of the other members of the same 'tribe'. If they oppose it nothing happens, if they ignore it or, worse, weakly support it, the situation deteriorates in a feedback loop until both sides convince themselves that everyone from the 'enemy' camp wants to kill them, so the only option is to kill them first.