I came across this site trying to look for genuine research into the causes of homosexuality and instead found this horrible case of conservative homophobia reinforced by liberal homophobia. The website is run by Muslim "researchers" who define sexual orientation as being based on gender identity (thanks, reluctantcommenter). I posted this before, but it was filtered out by Automod. A long-time lurker, I immediately made an account after seeing this site just to post it, but Automod wanted post history.

Particularly damning quote:

"Decades of research have not provided any clear genetic or hormonal mechanisms that would mean homosexual men are born “feminised” or homosexual women are born “masculinised”. What we do find however is that the gender identity of homosexual individuals in childhood, is significantly disrupted as a result of dysfunctional relationships with heterosexual role models of the same gender and members of the same-gender peer groups. This demonstrates that homosexual orientation is dependent in such cases, not on biological gender differences, but on psychological gender differences. This supports the notion that homosexuality is the product of a psychological gender-identity disorder, born out of a failure to identify and receive acceptance from other members of the same biological gender group, whether they be parents or peers. Sexual orientation is only one part of this gender identity disorder. This is demonstrated by the fact that gender non-conformity in childhood is the most powerful predictor of later homosexuality. This development of a psychological gender-identity of the opposite sex, as evinced by childhood gender non-conformity, strangely demonstrates that gay individuals are actually expressing a heterosexual orientation through their homosexual desire. The same goes for gay women, vice-versa. Since they psychologically consider themselves as belonging to the opposite sex, they develop homosexual attractions to members of their own biological gender. More than that, homosexual cravings are also it seems rooted in a desire for acceptance and affection from members of one’s biological gender, a desire that becomes sexualised with adolescence, resulting in early adolescent homosexual experiences."

TLDR: They assert that homosexuality is mostly caused by social factors such as peer rejection and having a bad relationship with one's parents, and is a "gender identity disorder".