[what's up]

I don’t understand why people kill others and have wars because of differences in their religious beliefs

No, this does not "clear it up". You also said along the same lines:

But I don’t understand why/how one’s belief in God can be used so effectively to rally people behind them

I just said that I don’t understand how or why people rally behind religious causes

The religious beliefs is what you were commenting on...why someone would fight for their religion. I gave you an example of why and then you said you understood it because it was simple, pretending like you had never not "understood". Instead of acknowledging that you shifted to a new topic.

[stuartcr]

OK, I do not understand why someone would fight for their religion.

Please repeat exactly what you said, perhaps I missed something. I will answer as best I can.