It's not about keeping your mouth shut. It's about knowing when the funny is appropriate and when it's not.

When I discuss theology and dogma and cultural bases for traditions, I don't want people to keep their mouths shut. A civil tongue in that head, yes, but not closed mouths.

On the other hand, when I post something along the lines of, "Hey, look, something I can be proud of as a Catholic and not have to deal with popular misconceptions fed by hierarchical idiocy," the smart-mouthed reply is not welcome.