I'm not Catholic and have no problem with calling a priest Father,
However, I did once have a friend who was reported by the local priest because she called him "sir" and not "Father".
She worked in the local post office. The priest corrected her. "Sorry, sir - I'm not actually Catholic so I can't do that," and he demanded to see the manager. That was a long time ago, however.
I'm not sure what the answer is.