Would you say "Yes" or would you say "I'm a Catholic"?
I would say yes, and then say that specifically I was a Catholic.
I would expect others to do the same -- say yes and then say specifically Methodist, Presbyterian, Baptist, or whatever they were.
Why? Did the Salvation Army ask if he was any specific denomination? No. The Salvation Army did not ask him whether he was a Catholic or a Baptist or a Methodist. They asked him whether he was a Christian. He chose not to directly answer the question, but instead stated that he was a Catholic. There are a lot of people who claim to be Catholics who would never claim to be a "Christian" lest they be identified with all those fundamentalist born-again fanatics.
Mr. Clark gave the wrong answer. He might as well have said no.
You might expect that however many Roman Catholics do not.
When a relative of mine (RC) was asked if I was a Roman Catholic he replied " No, she's a a Christian". Too sad.
But I would never answer that way. I've been a member of all 3 of those churches and a few others as we attend church depending on who preaches Christ and not what they're sign out front says.