I read it a few years back. The main theme of the story was that in the deep future, man has moved onto space ships completely and evolved further to a gravity free environment, having 4 hands and no feet.
Society however has massively regressed to the point where Sodom and Gomorrah would blush, but the people have no fear of a greater power or punishment in their mighty star cruiser.
However stories start to spread about rival ships that were just as debauched being destroyed in horrific ways for their cruelty and perversity, which are dismissed by most, as "If the ship was destroyed utterly, who is spreading the stories?"
The ship then picks up a stray castaway flashing his emergency broadcast into space. He is a quiet unassuming man and they mock him for basic decency, replacing his fluid ration with urine in front of him and proposing a toast.
In the climax the man removes his face, speaking a line to the effect of, "When the universe is infinite, man must have an infinite fear also, to keep him in line." Before annihilating the ship, sparing only the point of view protagonist to spread his story on another ship.
Can anyone remember the name of this short sci-fi story?