Our beliefs aren't just cargo that we carry around. They become part of our personal identity, so much so that we feel hurt if we see someone attacking our beliefs, even if the attacker isn't speaking to us individually. These "beliefs" are not necessarily grand things like moral frameworks and political doctrines, but can also be as inconsequential as an opinion about a song.
This post is for discussing times when you actually changed your mind about something, detaching from the belief that had wrapped itself around you.
Relevant reading: The Importance of Saying "Oops", Making Beliefs Pay Rent
What would you say about the range of variety of our species that has survived? Would things be less "bloody and complicated" if it were narrower?
We are quite diverse. Sometimes at least, this causes additional bloodshed. (Sometimes we don't need this kind of cause, we invent some other pretext.)
But, yes. A greater biological diversity generally means more reasons for a conflict.