[trigger warning: this comment discusses and makes comments on religion]
I agree that there should be a trigger warning for religion because weather you choose to blindly accept it as ruth or not, it can still be a sensitive topic. people argue over it, use it as an excuse to oppress people, and start wars over it.
I think if it just mentioned religion, or had a religious person in it, a trigger warning would not be strictly necessary, but if it make a statement about religion as a main point, that should have a trigger warning, true or not.
It's not that I think there is any problem with discussing religion or other sensitive topics in games, I simply think if someone is unwilling to have that discussion, they should have the option and ability to opt out.