I Drink Your Blood

A band of satanist hippies roll right into a city and start terrorizing the native folks. After raping an area woman, her grandpa goes after them, solely to be overwhelmed and compelled to take LSD. His grandson then plots revenge on the satanists by feeding them meat pies contaminated with blood from a rabid canine. They flip into crazed lunatics and start killing and/or infecting every thing of their path.