Woppy, Bill, though there might very well be a "gay gene", I wonder at which point the variants and degrees we are talking about (e.g. pedophilia) cross over from being a uncontrollable predisposition to a mere fetish.
There are straight guys, for example, that prefer sex a certain way, with a certain type of girl with certain attributes. I'll keep it tame...maybe favoring redheads, or Asian girls, or girls with large breasts. But these guys can, will and do have sex with other "types" and that sex is typically satisfying. A gay man having sex with a women is often not satisfying, and likewise to many can be downright repulsive (so I am told).
I think a large part of our main problem is that we long ago defined what is "normal sexuality", and we made everything else have some stigma and shame associated with it. Masters and Johnson studies from the 60s proved there is no such thing as normal, just a wide curve of varying preferences and predispositions.
TJR