The history of Christianity, the internal history of Christianity, is largely the history of people killing each other because they believed the wrong thing, and it's also involved in struggles with other religions, obviously starting in the Middle Ages, a struggle with Islam, in which, again, it was the infidelity, the fact that they didn't believe the right things, that seemed so offensive to the Christian world.
Так же это история о борьбе с другими религиями, начавшаяся в средние века с борьбы против ислама, который признали вероломным опять же из-за веры не в то, во что следует верить, а это для христиан оскорбительно.