Does Not Know Kung-fu
A character that believes in whatever, pick your fictional or real beliefs, having friction with another character who doesn't believe in that... that is called conflict and is what stories are about. Shying away from that doesn't make an RP better.So in my personal experience “religion” is just code for “bigoted beliefs that you aren’t allowed to call out.”
So I can see the mentality being “I don’t want to start unnecessary drama in the OOC”.
As religion is one of those things that people believe very strongly about IRL and it is not outside of the realm of possibility for whatever religion the character has to lead to fighting.
Either it’s disrespectful to a real religion, pushing an agenda people don’t agree with into the world, or people use it as a jumping off point to preach at people OOC.
So yeah I can see the GM being like “Nope I am not going to be refereeing petty infighting all day.”
If you have an RPer that is starting drama in the OOC, and you are the GM, step up and act like a GM.