I have always perceived it as a Mental illness but there are a lot of people who would justified it as a natural thing since it has been existing before the birth of Christ her on earth. Some will argue that Chaka zulu was gay, Alexander the Great was gay, Julio Caesar was gay and a few of our founding fathers.
They say it out of the normal and that is why so many view it wrong. and the Christian religion detest it.
IMO i believe it is a mental illness trigger by loneliness and rejection from females.