Opening on Friday in New York and expanding to other cities through the rest of the month in concert with Gay Pride, Daryl Wein’s Sex Positive is a documentary portrait of Richard Berkowitz, an early AIDS activist who helped to invent the concept of safe sex. Working as a team with writer/performer Michael Callen and doctor Joseph Sonnabend (the three collaborated on the groundbreaking 1983 pamphlet “How to Have Sex in An Epidemic: One Approach”), Berkowitz fought, largely without fanfare, to spread the word that a number of lifestyle factors (particularly, drug use and condom-free promiscuity) were responsible for the rapid-fire spread of AIDS through urban gay male communities. At his most active as an activist, Berkowitz was widely criticized (those who didn’t essentially accuse him of being a buzzkill tried to use his night job as an S&M hustler as evidence of his lack of credibility), and today his 2003 book Stayin’ Alive: The Invention of Safe Sex is out of print. Wein’s film thus seeks — and mostly succeeds — to canonize Berkowitz where history has failed to.