Because it takes a Mom and Dad to make a baby..not 2 dads or 2 moms
So if you believe it's a learned behavior, then why do straight parents produce so many gay children?
And to address your earlier post. Do you believe that you have to have sexual relations with the opposite sex to be gay?
Because what you are saying is that you can choose. Does that mean you can choose to have sexual relations with the same sex (because that's true) or do you believe you choose what sex you are attracted to?
Because if you do believe that, then you are attracted to both sex's and you choose to only be attracted to the opposite sex, right? It's a conscious choice you need to make?