This could very well be Freaks, a 1932 movie by Tod Browning. It has the title and the freaks (real freaks, which freaked the audience out — pun intended). It has been decades since I saw it, so I don't remember the butt-wiping scene; but then, the movie exists in several cuts, and the scene may be from a longer version than the one I saw.
The central story is of this conniving trapeze artist named Cleopatra, who seduces and marries the sideshow midget Hans after learning of his large inheritance. Cleopatra conspires with circus strongman Hercules to kill Hans and inherit his wealth. At their wedding reception, Cleopatra begins poisoning Hans' wine. Oblivious, the other "freaks" announce that they accept Cleopatra in spite of her being a "normal" outsider: they hold an initiation ceremony in which they pass a loving cup around the table while chanting, "We accept her, we accept her. One of us, one of us. Gooba-gobble, gooba-gobble". The ceremony frightens the drunken Cleopatra, who accidentally reveals that she has been having an affair with Hercules. She mocks the freaks, tosses the wine in their faces and drives them away. The humiliated Hans realizes that he has been played for a fool and rejects Cleopatra's attempts to apologize, but then he falls ill from the poison.
While bedridden, Hans pretends to apologize to Cleopatra and also pretends to take the poisoned medicine that she is giving him, but he secretly plots with the other freaks to strike back at Cleopatra and Hercules. In the film's climax, the freaks attack the evil pair during a storm, wielding guns, knives, and other sharp-edged weapons. After trying to kill seal trainer Venus and her clown boyfriend Phroso for knowing about the plot, Hercules is chased by the freaks in a storm and not seen again (the film's original ending had the freaks castrating him: the audience see him later singing in falsetto). As for Cleopatra, she has become a grotesque, squawking "human duck". The flesh of her hands has been melted and deformed to look like duck feet, her legs have been cut off and what is left of her torso has been permanently tarred and feathered.
This may be the "worm guy" you're thinking of: