To be fair, you started moving the goalposts by invoking special privilege/motivation for misaddressing people.

But to answer why I would be rude to christians for misnaming me, is because in my culture it is rude to misname people, and even more so when they've offered a good natured correction.

If you say you're William, and I call you Shirley, would you defend my right to call you Shirley?

And why would it be different if The Almighty Bob said to surely call you Shirley?