Dickass Motherfucker

Plural A derogatory comment usually but not specifically aimed at a homosexual or gay male human.
Due to the action of homosexual sex in a gay couple, of the thrusting of the "dick" in this case into the "ass" of another. Hence dickass motherfucker.
Motherfucker is used only as an insult endstop, to bring finality to the statement or insult.