Now, someone will come along and argue that 'orientation' is inborn, even if behaviors are chosen. But then, since we are thinking animals, even 'oreintation' is a fabrication of the mind. A pyromanic is 'oriented' to setting fires. Even if he doesn't act on his 'orientation'....he is nevertheless not mentally healthy. However, we have (as a society) decided that this particular deviation (and adult-child sex is the next one to fall) is not mental. One would have to have scientific evidence that it is genetic to draw such a conclusion. And, of course, there is none. Just as there is no gene for pyromania.
Homosexuality as 'normal' is nothing more than a societal compromise (defining deviancy downward) since there is no science to it.