Australia’s LGBT history gets thrown onto the barbie in a film similar in tone to last year’s “BPM.” Confrontational Lance Gowland (Damon Herriman) falls in love with the more conservative Dr. Jim Walker (Xavier Samuel). Leading the lesbians is outspoken Marg McMann (Kate Box). Their personal dramas are set within the larger context of the political movement between 1972 and 1978. It builds to the first Gay Mardi Gras in Sydney, which the police turn into the riot of the title. The main characters are real people who were involved in creating the event, which has continued annually ever since.