They wanted to intimidate you. By demanding you put it in writing, they'll get your name, address and congregation so they can mark you. They'd be smoking up the phone line in two seconds flat. You know, telephone, telegraph, tell-a-dub! Being straightforward and giving you a verbal answer takes away their opportunity to go after you later on.
You are supposed to read between the lines that you're on thin ice, asking impertinent questions like that, ha. They remind me of the sinister Scientologists.