The pattern of PIB will be familiar if you’ve ever discussed marriage equality with relatives, co-workers or fellow parishioners who oppose it, but can’t quite explain why. It’s not so much an argument as a defense of not having one: “Oh yeah? Well just because I can’t give a good reason why something should be prohibited doesn’t mean it should be allowed! After all, I can’t explain why polygamy, incest and bestiality should be prohibited either — so does that mean those should all be made legal too?”