It seems like in nature or on its own such a mindset would be akin to being in a death cult- you're just going to get rolled over by someone else and your "tribe" won't be around long enough to have this belief "reproduce" and be passed on.
But if you live in the midst of a society full of other people who are willing to kill or be killed to protect those in it beliefs like that can grow and gain followers without any risk of external challenge putting their faith to the test.
Reading my comment I realize it may sound a little bit inflammatory or perhaps bloodthirsty- that's not my intention, I don't know how to word it better. Just a passing thought on this topic