Agreed here, I didn't think I was until later in life when it hit me that most of what I believed was just because a parent or the church told me to. Most of the time these people when confronted will double down on their beliefs because questioning anything that has been said by a pastor/priest means questioning their entire religion. Even just asking why it's a bad thing causes them to retreat in and start loudly defending themselves because this is what the church teaches them to do. Warriors of god and all that indoctrination.

OP best thing IMO is to just state matter of factly that "Just because you believe this doesn't mean everyone else does" (not questioning them or anything just clear messaging) and that it is offensive to you. They are trained to argue and defend themselves, shut that shit down. You can also avoid them, but it does push them further into their beliefs. Catch 22 there