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.
This is sheer idiocy.