Homosexuality is sinful in all major monotheistic religions. Christianity, Judaism, and Islam all have rules/ regulations/ laws designed to help people resist temptation.
One hundred years ago, anal penetration of another man was grounds for life imprisonment in Canada and other countries. There was no jail sentence for being the bottom; that was considered a victim of sodomy/ buggery.
Human civilization is still very recent, in evolutionary terms. Certain behaviors that are considered 'aberrant' 'perverted' or 'taboo', (traditionally,rape, incest, bestiality, necrophiia, and homosexuality), are described in the book of Leviticus in the Old Testament of the Bible, with the original penalty.
These 'sin crimes' involve temptation, in that, the perpetrator knows that the act is either illegal, frowned upon, or dangerous, but he does it anyway, because he thinks with the little head.
No one can be 'born gay'. That's impossible; human beings don't have instincts. Unless one is being gang raped by multiple assailants, no one is forced to engage in a sexual act, whether it be heterosexual, homosexual, or autosexual. It's a choice made with free will.
Some men, and women, ARE born with more curiosity about sexual partners of their own gender, but engaging in any consentual sexual act means that the choice was not preordained by genetics.
Some men, (peace for example), are born less masculine than others, but that does not necessarily mean that they will be someone's bitch - it does, however, make that possibility more likely. Let's face it, many women like gay and effeminate men as friends and confidants, but they would never sleep with them; they have asexual status, like a Ken Doll, in that woman's perspective. These 'girly men' sometimes have sex with women, but usually with disastrous results, and they often pair up with a 'bird of the feather' guy friend who also has no game.
Some men become gay because they are clueless with respect to the unwritten rules of male interaction. They are the snitches, at a young age, or the boys who are indiscrete, being unable to keep a confidential piece of information quiet. These guys become gay because they are ostracized from the male circles of influence, so they have to bond with the females, and the other exiles.
Some guys become gay because they're physically, mentally, or emotionally lame. They have no strength or coordination, and the least amount of physical pain makes them cry. They 'wimp out' at dares, or tasks that require dedication. They have lame taste in music, compared to their friends, or they enjoy activities not deemed to be masculine. These guys usually become bottoms. In addition, there are those who are recruited, by pedophiles. These are usually small, naive kids, or post pubescent teens, with much curiosity, and little knowledge or experience. A friendly older man parties with them, serves them alcohol, shows them pornography, and makes them gay.
No one is gay until during or after they commit a gay sex act. Ipso facto, no one is born gay. They become gay. Where and when that happens varies.