It’s about this guy who keeps getting screwed around by old people. Fed up, he goes on a major campaign to kill all people over the age of… 50? (or something like that) In which he eventually succeeded.
Wild in the Streets was late 60’s, but is also what came to my mind. I still have the hit record from the movie: The Shape Of Things To Come by “Max Frost And The Troopers” (I think it was really Davie Allen and the Arrows); the onscreen band’s drummer was played by young Richard Pryor.