[bk1000]

"Show the proof that a god exists. What device can measure and detect it?"

This is not the point. If man were made by some factory or assembly line, the author's point would still be valid.
All humans (except for the aforementioned rare hermaphrodite)
are indeed psysiologically heterosexual. Sex is by nature intended for reproduction. Homosexuality is strictly recreational.

[Greenback_dollar]

Excellent post, I agree with you whole heartedly (although heterosexual sex can also be recreational).

A man is a man because of physiology; by definition he must have certain characteristics that physically define him as "male." When a man is stimulated sexually, he is aroused in the traditional sense. The cause of that arousal is the crux of the issue.

If the stimulation is a result of homosexual attraction or if the stimulation is the result of heterosexual attraction the end result is the same. (As Wayne and Garth would say SCHAWING!). The physical body was designed to respond to simulation in the same way.

So regardless of internal preferences, external responses have to be the same.