Then there's such a thing as a "bidden" thought: one which one does not resist, or which one welcomes, calls to mind, or which one dwells upon, or settles into as a lustful fantasy, or worse yet, a plan. This is a sin: a sin of intended lustful thoughts. Any action consequent to it, like masturbation, is also a sin.
The first, inadvertent temptation, is not a sin. Scripture says Jesus was tempted in every way as we are are, but without sin.
If something enters your mind and you do not dwell on it, sin has not occurred. Or to talk about it as we are would be impossible without it being in your head. But when you start to desire something that is evil you have entered the realm of sin. To desire to murder is sin, whether you do it or not. To desire homosexuality is sin. To try to say a person is “oriented” homosexual but not desiring it is the same as saying someone who is fat does not desire to overeat. Clearly they do desire it. The not desiring it part is more about regret and overview — “I do not want to be like this.” Read Romans 7. Sin is a battle for everyone. It is still sin.
Again, if we are going to use the term orientation for sin, then let us be consistent and use it for all sin.
Furthermore, to claim that one is “oriented” in a way completely opposite of their physical self does not make logical sense. Your best ground is when you call it a disorientation. I am not crazy about that either in that it still seems to be an accommodation different that other sins get. That puts it more in the mental illness category rather than the sin category.