And remember also that membership in the Catholic Church is voluntary, as is obedience to church rules.

Hmmm. As a bald statement I suppose that's true, but all is not what it seems. As with some other major organised religions, your membership is not voluntary. You're signed up virtually as you leave the womb. I was a baptised Catholic before my umbilical stumpy bit had dropped off. From then on, parents/grannies/uncles/teachers/priests/community spend much of your childhood and adolescent years making sure you are, at best, going to find it bloody awkward to get out (even if you've managed to resist all the brainwashing). It's a damn sight easier just to go along with it. It swells the numbers the Catholic church claims to have under its wing (which is the main point of it, really), but t'ain't right, is it.