Theists and atheists are primed to dislike each other. It’s a function of the labels. Whenever people create an in-group/out-group dynamic we progressively identify more with the in-group and consider the out-group the enemy. It seems to be human nature--whether you think that nature is due to the fall of man or selective pressure.
I am an atheist, I’m not denying that, but I’m tired of it opening the door of generalization. I probably don’t possess whichever negative qualities someone draws from whichever other atheist they happen to dislike the most. I’m an individual. So are you. So is that Christian. So is that Muslim.
Now I’m buried in labels--secularist, naturalist, materialist, evolutionist, New Atheist, Darwinist, humanist, skeptic, whatever. I honestly don’t know if there are distinctions any more or which really do apply.
People's obsession with this or that sports team relies on one of two factors the vast majority of the time. You root for team "X" because you either are geographically located near team "X" or your parents root for team "X." Of course, the same two factors play a heavy role for religious preference. Do most people you know practice the same faith as their parents? That may be anecdotal evidence, but statistics show this as well. It's impossible to argue that Hinduism isn't primarily practiced in Indian. Muslims and Christians have spread out some, but have pretty solid majorities in specific areas. "Jewish" as a term is so entrenched in cultural heritage that it identifies ethnicity every bit as much as it does faith
You probably think it's silly for me to say that the Ohio State Buckeyes is the objectively right team, but that is what the religious are do. It's important to consider that one's belief in Jesus, Yahweh, Allah, or Vishnu is more dependent on convenience than correctness.