Query: When did protesters run into the outfield and try to set fire to the U.S. flag?
Context: On April 25, 1976, at Dodger Stadium, father-and-son protestors ran into the outfield and tried to set fire to a U.S. flag. When Cubs outfielder Rick Monday noticed the flag on the ground and the man and boy fumbling with matches and lighter fluid, he dashed over and snatched the flag to thunderous applause.