How about "I burn heretics whenever the opportunity presents itself" posted on the door. If that doesn't work answer the door with a jerry can.
C'mon folks cut the Mormon's some slack. If we elderly types didn't have Mormons banging on our door every saturday morning what would we do for the weekend entertainment.
Hell, they're more reliable than most of our children. They never phone with all that clap trap about being to busy to visit, that the kids are sick, or that they'll try stop by next week, which, as we all know never happens.
The one thing you can count on is the Mormoms. They always come once a week, rain or shine to keep us entertained with their litany of god knows what, and the best part is that since they invented the volume control on hearing aides they aren't all that annoying anymore.