You're half right, but dismissing it as a choice is naive. Vast evidence shows that homosexual tendencies are the result of emotional relational issues implanted very early in life, long before it occurs to anyone to make a choice. The choice comes when a person recognizes their inclinations and decides whether to challenge or embrace them.
That said, there might be some sort of genetic component that makes a person more inclined to indulge in homosexual behavior as a response to their emotional issues where another might engage in substance abuse.
Regardless of our inclinations, mentally stable people are able to control their actions, thereby meaning that all of our actual behaviors represent a choice on our part.
see post 76. Dismissing it as a choice is not naive. Whether or not certain external social factors led one to homosexuality does not negate the fact that that homosexual chose his path. Plenty of straight guys lived with the same types of factors and chose to avoid the appeal of the unnatural and perilous lifestyle.