You say orientation isn't a choice even though bisexuals at least establish it as their free choice for relationship. Fine. Even if you correctly claim that some people may have an immutable orientation, why would you in your brilliant and far reaching wisdom think it would be inhumane for the same person to be celibate from that orientation? And further think it is inhumane for the person to engage in a relationship of another orientation?
I don't believe for a second any person has this immutable orientation, straight or gay. And likewise, I don't believe it is inhumane for a person to avoid a relationship that is illegitimate. Trying to argue otherwise is like arguing the color blue can also be seen as red.