It seems that your argument presupposes the existence of God, does it not? If there is no God, then the logical-moral connection breaks.
Perhaps I am being dense, but I still think you are making a number of jumps. First, it is a jump to say that homosexual sex is illogical. It’s certainly not illogical by the participants, their logic for wanting to do it is quite clear and cogent. I can’t think of any other way to even evaluate the logic of an act. Both Laurie and I have brought this up, and you haven’t resolved this issue.
Second, I still don’t see how just because it is illogical means it is immoral. Why couldn’t God allow something that’s irrational and yet moral? I’ve read through your previous post several times, and I still don’t understand.
Further, by the same view, is not kissing per se immoral? Our mouths are clearly not intended for putting them on each other, so by your definition, kissing would be illogical, and because it is illogical, it is immoral.