It is probably wisest not to openly disagree with a friend over topics which are neither here nor there in my daily life. At such a point, ego and maybe primitive fight modes kick in (even if only in a verbal manner). People, like dogs peeing on fire hydrants, sometimes stake their territory for the sake of staking their territory. It is something that I occasionally have to remind myself of. Let them have the fire hydrant. It is best to choose our battles carefully.