You wanna go to war?
Just like what occurs in actual wars and even the wars of Pepsi vs. Coke, McDonalds vs. Burger King, Raiders vs. Classiness, and Cowboys vs. Intelligence, this "us against them" mentality in Christianity is ultimately designed to benefit someone.
Although it appears that the people who are standing strong waving the banner for their preferred choice will benefit, which they usually have been heavily marketed and manipulated into choosing even in churches. Usually the benefactor(s) is(are) the source(s) of the division.
How much has been made, in various ways, off the backs of people that have been led into going to war over trivial issues, or trivial choices, that have been carefully, meticulously, crafted, and manipulated into being a catalyst to war with a fellow man over.
Something to think about.