The campaign to end marijuana prohibition received a noteworthy endorsement last week, when the head of the second-largest teachers union in the country said that she supports this year’s ballot initiative in California to regulate marijuana. Randi Weingarten, president of the 856,000-member American Federation of Teachers, told HBO’s “Real Time” host, Bill Maher, that “everything in moderation is pretty much fine.” “When something becomes a forbidden fruit,” the 52-year-old told Maher, “you have…