Sean Penn isn’t quite the public speaker that Harvey Milk was, but that’s about the only shortcoming in his knockout performance as Milk. He still manages to get a certain lascivious twinkle in his eye as he scatters double-entendres on the assembled multitudes. Penn and director Gus Van Sant opted to have the actor go deep into character as the legendarily charismatic San Francisco gay rights martyr – wavy hair, lopsided grin, polyester suit, and all. The strategy succeeds, and so does the film.

Milk is a bracingly passionate look back at the man who helped define a specific era of the late 1970s in the Bay Area, when the aspirations and fears of gays, lesbians, and a rainbow coalition of working people were crystallized in the inclusive political message of a community organizer who ran a camera shop in SF’s Castro district. The message was about hope combined with a sense of humor, and Milk captures it with maximum local flavor.

For most audiences, especially younger ones who somehow missed the history, the film’s vivid evocation of the awakening of multiculturalism will be enough. It’s told as a flashback from the day in 1978 when SF city supervisor Milk, along with liberal mayor George Moscone, was assassinated by reactionary former supervisor Dan White. From that base line, we’re plunged headlong into the full ‘70s: the Stonewall riots, homosexual hippies furtively kissing in the subway, nascent gay liberation, and the transformation of the Castro from a square Irish-American neighborhood into the world’s gay mecca. The latter was greatly helped along by transplanted New Yorker Milk and his friends, who are shown tirelessly building their constituency, first to oppose discrimination and then to tackle the really important issues – like cleaning up the city’s dog shit.

Harvey Milk’s genius was in relating to everybody, not just gays and lesbians, around basic, urban quality-of-life issues, but with an edge. Union officials, in particular, admired the way Milk and fellow activists engineered the successful Bay Area boycott of Coors beer, something they had not been able to do. For them, the issue was Coors’ anti-unionism; for gay organizers, it was the Coors family’s homophobia. Milk showed how the two groups could rally around commonalities. That free-form coalition building became his ticket to power. Van Sant wisely uses Rob Epstein’s brilliant 1984 documentary, The Times of Harvey Milk, as a template.

Penn’s performance is one of the smartest in his ambitious, risk-taking career. He captures the mercurial Milk – warm and cuddly one moment, coolly vindictive the next – a quick-thinking, fast-talking guy with a talent for disarming almost anyone. His inner circle is portrayed by a roster of Hollywood pinup boys: James Franco as lover Scott Smith; Diego Luna as the other, crazier lover, Jack Lira; and Emile Hirsch as Milk political aide Cleve Jones.

Throughout, Van Sant pays loving attention to the cultural details of the time. After all, they’re more or less the details of Van Sant’s career, as well. From the white-brown male romance Mala Noche in 1985, through Drugstore Cowboy and My Own Private Idaho to the schoolboy legends of Elephant, Last Days, and Paranoid Park, filmmaker Van Sant has charted a succinct but deliberately homoerotic course through a neglected subtext of the American experience. He admires troublemakers. Harvey Milk fits the mold perfectly, even though Milk uncharacteristically tackles (you’ll excuse the expression) a straight historical subject. Milk became a legend even before his untimely death – that’s undoubtedly what appealed to Van Sant. He, Penn, Brolin, and company wallop Dustin Lance Black’s carefully respectful screenplay about an inspirational civil rights leader into another realm entirely. And what a perfect image for Milk’s last sight: the San Francisco Civic Opera House and a banner for Tosca. But the ongoing struggle stubbornly shines through – just as Milk and his followers battled Anita Bryant and her homophobes with their hateful Proposition 6, more or less the same thinking is behind the current Proposition 8. The more things change…

MILK (3½) Directed by Gus Van Sant. • Starring Sean Penn, Emile Hirsch and Josh Brolin. • R, 128 min. • At the Osio Cinemas.