Satan's Children (1975)

Sinopsis: Bobby is a troubled teen with problems. After deflecting his father’s insults and his stepsister’s come-ons, Bobby unknowingly ends up at a gay bar. Before long, he’s assaulted by four guys in the back seat of a car. With nowhere else to turn, Bobby joins a cult of Satanists to enact his murderous revenge, but his presence leads to conflicts within Satan's Children, especially after a lesbian member is damned to Hell. But Bobby proves to be one sick puppy, which he demonstrates in ways that would even make the devil smile. So hilarious, and just plain insane, you'd think Lucifer himself was personally involved!