“I don’t believe anyone is really gay,” Joseph Nicolosi told the New York Times in 2012. “I believe that all people are heterosexual, but that some have a homosexual problem.” Nicolosi, a psychologist, had by then written four books, with titles like Healing Homosexuality and A Parents’ Guide to Preventing Homosexuality. In 1992, he founded the National Organization for Research and Therapy of Homosexuality, or NARTH, an organization of psychologists that aims to help gay people “realize their heterosexual potential” through a practice that is alternately known as “conversion therapy,” “reparative therapy,” and “reorientation therapy.” Nicolosi died on Thursday, March 8, at age 70; NARTH’s announcement said that the cause of death was the flu.

Before NARTH’s founding, there was a small but violent history of gay conversion attempts by doctors and psychologists. In the early 20th century, Freud made attempts using hypnosis. In the 1950s, Edmund Berger advocated a “confrontational therapy” approach to gay patients, which consisted of having practitioners yell at them that they were liars and worthless. Other attempts to convert LGBT people to heterosexuality throughout history have included methods like lobotomy, electroshock to the hands, head, and genitals, testicle transplants from dead straight men, “bladder washing,” castration, female circumcision, nausea-inducing drugs, and beatings. But it was Nicolosi who brought gay conversion therapy into the mainstream, popularizing it among religious communities and the American right, and turning what was once a scattered practice of abuse into a multi-million-dollar worldwide industry.

Nicolosi grew up in New York; he received a master’s degree from the New School and spoke in a thick Long Island accent. But he spent his career in Los Angeles. He received a PhD in clinical psychology from an obscure school there, and opened his own clinic in Encino in 1980. He seems to have focused his practice entirely on gay conversion attempts. The time was ripe. The social movements of the 1960s and the gay rights activism that flourished after the Stonewall Riots in 1969 ignited profound fear on the American right. Nicolosi found an eager audience for his claim that heterosexuality and traditional gender conformity were not only superior, but that deviations from them were pathological.

The field of psychology had never been particularly welcoming to queers, but by the time Nicolosi began practicing, attempts to convert gays had already been relegated to quackery. Freud wrote that the prognosis for heterosexual feeling in homosexual patients was grim (though he did believe that gay impulses could be reduced under some circumstances). In 1932, Helene Deutsch published her study “On Female Homosexuality,” which recounted Deutsch’s attempts to instill heterosexuality in a lesbian, only to find that her patient had begun a relationship with another woman while the study was ongoing. In her conclusion, Deutsch noted that a straight relationship would have been her preferred outcome, but also seemed to acknowledge her patient’s lesbian partnership as psychologically healthy.

In 1948, just a year after Nicolosi was born, Alfred Kinsey published his groundbreaking report Sexual Behavior in the Human Male, which found that homosexual tendencies were much, much more common than had previously been assumed. In 1978, the American Psychological Association removed homosexuality from its list of clinical disorders in its Diagnostic and Statistical Manual. Anti-gay stigma and bigotry were still rampant, both within the culture and within the field, but establishment psychologists had given up conversion attempts as a lost cause.

What Nicolosi offered was a way for homophobic parents, patients, and psychologists to validate their anti-gay feelings as being legitimated by nature, science, and psychological evidence. He established NARTH in 1992 alongside Benjamin Kaufman and Charles Socarides, two other obsessively anti-gay psychologists, explicitly in reaction to the removal of homosexuality from the DSM. They spoke in appealingly professional jargon, using phrases like “trauma” and “bad attachment.”

The organization became a network for homophobic psychologists, as well as a link between the industry and the growing number of ex-gay ministries and “pray away the gay” programs on the Christian right. Nominally secular, NARTH and Nicolosi frequently embraced religious rhetoric and prayer tactics, and were listed as ministry partners by a number of homophobic Christian organizations. The Thomas Aquinas Psychological Clinic, where NARTH is headquartered, is named after a Catholic saint. “We, as citizens, need to articulate God’s intent for human sexuality,” Nicolosi told Anderson Cooper in 2007. That same year, he told an ex-gay conference, “When we live our God-given integrity and our human dignity, there is no space for sex with a guy.”

Nicolosi’s treatments often involved multiple one-on-one sessions per week. According to accounts given by former patients, he seems to have used a mix of Berger’s “confrontational therapy” methods of emotional abuse with what’s known as aversion therapy. Aversion therapy applies pain or discomfort to patients in conjunction with homosexual impulses or behaviors: Everything from snapping a rubber band around a patient’s wrist to giving them electric shocks to making them vomit. He believed that gay people had bad relationships with their parents in absolutely all cases, and spent a great deal of therapeutic time probing patients for incidents of humiliation, neglect, or contempt in their childhoods.

For unclear reasons, he also believed that viewing pornography could cure homosexuality, an idea he repeatedly defended to professional gatherings. Programs associated with NARTH have been found to administer beatings to their patients. The majority of Nicolosi’s patients, like the majority of conversion therapy victims generally, were children and adolescents, forced into his care by parents who were bigoted, sadistic, or merely scared. Nicolosi encouraged these impulses; he claimed to be able to identify and reverse homosexuality in children as young as three. In his books, he instructed parents to monitor their children for supposed early signs of queerness, including shyness or “artistic” tendencies in boys.

But even before Nicolosi died, NARTH was facing a host of challenges. It lost its nonprofit status in 2012, and an important accreditation from the California Board of Behavioral Sciences was revoked in 2011. Prominent members of the group have been embroiled in controversy, including George Rekers, a conversion therapy psychologist who was discovered to have hired a 20-year-old male sex worker in 2010. California outlawed the practice for minors in 2012, cutting deeply into NARTH’s L.A.-based operations; New Jersey, Illinois, New York, Vermont, and Oregon have since passed their own bans. But the group and its imitators continue to harm both children and adults.

Discovering that you are gay, or that your child is gay, is frightening. It means confronting a future that will not look like the one that you expected, and it means realizing that you and people you love will be subjected to stigma, discrimination, harassment, and the punitive whims of the state. It means staring down a life with fewer certainties and more vulnerabilities than a straight person’s. Scared and misguided people went to Nicolosi for help, and he exploited their fear to perpetuate hate, inflicting horrible pain and incalculable psychological damage on his victims in the process. It is unfortunate that his legacy won’t die with him.