Tradition! Tradition! (Tradition!) Love 'em or hate 'em, you can't live without 'em. In Stranger in a Strange Land, Mike finds himself constantly in opposition to the customs of humanity. His Martian mind can't comprehend why people would see things—say, cannibalism—differently than he does. Meanwhile, other characters, even Mike's companions like Jill and Ben, are unknowingly under the power of tradition. It guides their actions, putting them in opposition with Mike for reasons they themselves don't fully understand. Enter Jubal Harshaw. Jubal's willingness to question the "common sense" reasoning behind tradition and custom allows him to see beyond the tyranny of custom. And his crotchety old man attitude means you know he'll tell everyone what's on his mind.
Ben did not alter his customs when joining the Church of All Worlds. His lifestyle before joining followed the same rules of sexual promiscuity and individualism—joining just made him realize this fact.
The carnival is the closest the novel comes to presenting a custom-free society, since the carnival must blend its customs to those of the town it is visiting.