Gays can't become ungay?

Question for the 4channer community: Do you think it's entirely NOT possible at all, not even in the least to be aroused by a women if you are gay? Obviously not all "gays" are exclusively attracted to other men, they do have some physical interest in women, correct? (Being "bi"). A study I came across once suggested that most men (and women) have a partial attraction to both sexes, by measuring blood flow to parts of their body when exposed to certain scenes and or images.

So if many men and women are atrracted to both, does that mean that there are some men that are 100% incapable of getting or maintaining an erection with a female, and actually having sex with them? The reason I ask is because if even a few men are like that, how could it possibly be claimed that sexual preference is based on emotional factors and growth as well as your physical make up? I personally believe that your body tells you what you wish to mate with. How else would you explain the reaction of blood flowing to the right parts and hormones that react to certain stimuli? You don't choose to have an erection at all times, your body does it for you.

tl;dr version: Is there even ONE man on earth who can't keep a boner with a girl or have sex with her?

I must admit that there is nothing more attractive than a hairy, sweaty, shit-caked cowboy rectum. Makes me want to slide my manhood right in that pooh hole and start packing the fudge! If my guy has a few HIV shankers oozing puss, so much the better! Why would I want to screw a dog like Jessica Alba when Gaylenhaal's butt is so mighty fine?