Reviewing the most up-to-date independent research, both McHugh and his colleage concluded that there are many myths about homosexual behavior. Most notably, McHugh found the "born that way" theory is not supported by any of the studies.

In response to McHugh's research, LGBT advocates have set their sights on him as a "bigot." One blogger commented that McHugh's research is simply a straw man for his "bigoted beliefs" and claimed he is a "scientist who appears far too invested in his own antiquated, disproven theories and his anti-LGBT political position."

On Thursday, the attempt to discredit McHugh reached its high point. Dr. Lauren Beach, director of LGBT Research at Vanderbilt, released a letter with signatures of more than 600 "experts on LGBT health" to attack the doctor. In the letter, Beach questioned the integrity of the New Atlantis as being a "non-peer reviewed bioethics magazine." Beach further seemed to accuse McHugh of causing harm and pain to those suffering from gender dysphoria.

The letter added, "A substantial body of research points to stigma and its consequences as contributing to the mental and physical health disparities among LGBTQ people."

In reponse, McHugh told reporters, "I'm 85 years old. I'm a university professor. I'm a member of the Institute of Medicine. I'm a person who has been through a lot of crazes before. I'm not going to my grave not having spoken my mind, OK?"

As chief pyschiatrist at Johns Hopkins School of Medicine, McHugh was responsible for putting an end to sex change surgery there, noting that he'd "witnessed a great deal of damage from sex reassignment." The school last year reversed the decision, andn plans on resuming sex reassignment surgery after a hiatus of 40 years.

In the letter, Beach concluded, "In summary, as researchers and clinicians with expertise in gender and sexuality, we affirm that the 'Sexuality and Gender' report does not represent prevailing expert consensus opinion about sexual orientation or gender identity related research or clinical care."

To this, McHugh said, "I see they don't like me. They've got an army of people that want to say so."

McHugh further rebuffed the attack on his study in The New Atlantis. "It's true it's not in a peer-reviewed journal, but it's not intended to do that," he explained. "It's intended to be published in a journal of opinion in which the public can view what we think about the contemporary scientific literature just like articles in The New Yorker or The Atlantic."

In January 2017, McHugh along with Michelle A. Cretella, president of the American College of Pediatricians, and Quentin Van Meter, vice president of the American College of Pediatricians, published an article stating, "A person's belief that he or she is something they are not is, at best, a sign of confused thinking."

The article continued, "Conditioning children into believing a lifetime of chemical and surgical impersonation of the opposite sex is normal and healthful is child abuse."

At the time McHugh published "Sexuality and Gender," Johns Hopkins distanced itself from McHugh's research after threats from LGBT activists.

The aggressively gay Human Rights Campaign warned the Baltimore-based university, "If Hopkins' leadership ignores their community's call to correct the record -- clarifying that McHugh and Mayer's opinions do not represent it, and that its healthcare services provided reflect the scientific consensus on LGBTQ health and well-being -- its Healthcare Equality Index score will be reduced substantially."

The dean of the Medical Faculty, Dr. Paul Rothman, issued a letter in response to the Human Rights Campaign stating, "When individuals associated with Johns Hopkins exercise the right of expression, they do not speak on behalf of the institution."

Among other findings in "Sexuality and Gender," McHugh frustrated the narrative that non-heterosexual activity is purely biological. The report states that based on the 11 independent studies, "biological factors cannot provide a complete explanation" of homosexual behavior.

"Sexuality and Gender" also reveals that "lesbian, gay and bisexual individuals had a 2.47 times higher lifetime risk than heterosexuals for suicide attempts." The report called for further research about the psychological origins of LGBT behavior.

McHugh is also notable for having sat on the U.S. Conference of Catholics Bishop's National Review Board for the Protection of Children and Young People in 2004, concluding from the investigation into clerical sex abuse that it was essentially "homosexual predation on American Catholic youth."