People often over relate to a group, so their ego can take credit for traits within the group abstraction, even of they don't deserve it. For example, a white supremisist might say Albert Einstein was white therefore whites are smarter. That white association makes him smarter by association. Since his team is the best he is also best.
Say we related to being human. I might say humans would survive if the earth underwent a major change and culture was destroyed. The truth is some humans would survive. But most would lack the ability to cope or adapt. If the person is relating to being human, he can personally accept credit for this survival scenario, due to the group abstraction. This is true even if he personally would not survive.
Since the ego can become dependent on the abstraction for some extra ego inflation, this same group association can make one vulnerable to ego deflation. If you insult a group, you can insult all the egos in the group, who are trying to inflate within the group abstraction. If I say humans are inferior to martians, this makes it harder to accept as much credit for the abstraction's survival card, causing the ego to deflate. To avoid this deflation we may need to fight or insult the other group abstraction.
This is not only true of religion, but to all group abstractions.
so the argument "we should get rid of religion because religion causes war" effectively becomes "we should get rid of group abstractions because group abstractions cause war" .... which then brings us to the essential role religion plays in diminishing group abstractions ....