When you're righting over religion, people are very reluctant to convert (which is usually a sin), and to accept the converted, so it ends with cleansings and genocide. Same thing with ethnic conflicts, but they're religion-driven more often than not.
If those two things aren't identical, then you have two or more different substantove belief systems that happen tobshare a common label; it's inaccurate to judge everything going under the label by either the founding philosophy or any of the later incarnations; they are separate things that must be judged separately.
We assume that we should stick with that Jesus considered right. But we can't ask him, so we have to interpret whatever sacred texts available. We assume that only one interpretation is correct and all other are sinfully wrong.
This is a fertile ground for conflict. Everyone has their own interpretation but pretends that they all share it. Ultimately it's the Highlander, when just one Christian is to stay alive over dogma.
This is actually stricter than Islam where conflicts over interpretation are explicitly discouraged, and indeed there's less of those. However Islam is even less tolerant to "live and let live".
The solution, IMO, is stop considering one person "the one", and get rid of sacred texts.