But it applies to no other Christians? Please...
But it applies to no other Christians?"
Other Christians aren't obligated because they do not recognize the authority of the Catholic Church. That's a topic for another time.
"Please..."
What if I told you it was possible to have a civil and Christian conversation without resorting to sarcasm or snarkiness? I don't know about you, but it's been a long time since I was in Junior High.