It wasn’t so long ago that gay men were vilified by American society at large. In the 1980s, when the AIDS epidemic surfaced, priests railed against gays, claiming the disease was God’s revenge for sinful lifestyle choices.

That, for the most part, has changed. HIV/AIDS is no longer the scourge it once was, and those with the virus  are living much longer. Many Americans support same-sex marriage, now legal in a number of states.

If there is one person responsible for this shift in mindset, it’s the outspoken activist, author and playwright Larry Kramer — the subject of a powerful new HBO documentary premiering Monday, June 29.

Larry Kramer photo/courtesy hbo

“Larry Kramer in Love and Anger” is accurately described as a “warts and all” biography of a passionate man who because of his take-no-prisoners attitude managed to alienate almost everyone — gays and straights alike — on both sides of every issue on which he took a stand. But as the film makes clear, were it not for his courage and confrontational style, many more lives would have been lost to the AIDS crisis of the ’80s.

Kramer was born in Connecticut in an unhappy Jewish home. His father constantly berated him, calling him a “sissy” and urging him to behave more like his athletic older brother. Kramer’s life became so untenable that while a student at Yale, he attempted suicide.

Early in his career, Kramer worked for Columbia Pictures. He was nominated for an Academy Award in 1969 for his screenplay of D. H. Lawrence’s “Women in Love,” and his musical adaptation of “Lost Paradise” was a financial success.

But Kramer felt movies weren’t the right platform in which to explore homosexual themes. After a brief and largely unsuccessful foray into theater, he wrote the novel “Faggots,” inspired by his experiences living on Fire Island, a summer haven for gays off the coast of Long Island, New York. The main character, Fred Lemish, loosely based on Kramer himself, was tired of the promiscuous gay lifestyle and was searching for love.

The book was pilloried in the gay press, which claimed it painted a negative image of gays and their lifestyle.

In the early ‘80s, Kramer’s friends became sick. Many died of Kaposi’s sarcoma, a rare form of cancer that seemed to hit gay men. Formerly disabused of political activism, Kramer banded together with some influential gay men and formed the Gay Men’s Health Crisis, which became the largest organization providing assistance to men with HIV/AIDS.

It wasn’t a good fit.  Kramer was far more strident than his fellow GMHC board members, calling out politicians and bureaucrats for not doing more to find a cure.  His sometimes over-the-top militancy created a schism with other GMHC leaders. When Kramer wasn’t invited to a meeting with New York Mayor Ed Koch — one of his frequent targets — he threatened to quit. His resignation was accepted.

Frustrated, he fled to Europe, where he visited Dachau concentration camp. Like many Jewish men of his generation, Kramer was impacted by the Holocaust and believed he was witnessing a Holocaust against gays.

Deeply moved, he settled in London and wrote the first draft of what became “The Normal Heart,” a largely autobiographical play in which Kramer rages against the straight establishment and gay leaders for their passivity.

The play, about subjects swept under the carpet at the time, was brilliant, moving and brave. It had a lengthy run off-Broadway, followed by numerous productions around the world, a recent Broadway revival and a 2014 HBO film that won an Emmy.

But progress in the real world remained slow. In 1987, Kramer was part of a group that formed ACT UP (Aids Coalition to Unleash Power), which used civil disobedience as a tool to roust naysayers out of their slumber. Yet even here, Kramer’s confrontational style stood out, as the documentary shows.

Many scenes toward the end of the film were shot in 2013 and depict a frail Kramer, hospitalized with complications from liver damage. (Kramer was diagnosed as HIV positive in 1988 and was the recipient of a liver transplant.) At his hospital-bed wedding to longtime companion David Webster in 2013, Kramer was too weak to say “I do.”

Filmmaker Jean Carlomusto paints a portrait of a provocateur who would not let anyone or anything stand in his way.

“Larry Kramer in Love and Anger” premieres at 9 p.m. Monday, June 29 on HBO