Your "non-sequitur" is trying insinuate that a person's innate sexual orientation toward certain genders mirrors an innate sexual response to certain body parts, which I don't disagree with. I find women beautiful, and in the right circumstances, I have a sexual response to that beauty. The difference lies between simple attraction and horniness.

I'm attracted to a beautiful woman wearing clothes that compliment her beauty. Do I immediately get a hard on? No. Do I become unable to function as a result of seeing her? No. Whatever reaction I have toward her beauty is my own circumstance to handle - she is under no obligation to change herself based on my reaction. I'm attracted to her, but seeing women wearing well-fitting clothes is a normal part of my day, so I don't find it overtly sexual. It can become sexual if the woman starts flirting with me, for example, but just wearing nice clothes doesn't make me horny, because most women wear nice clothes simply because they want to.

I see my wife topless all the time, and while I think she's beautiful, I don't get horny at every sight of her, nor should I. Most of the time she just doesn't want to deal with putting a shirt on - she's not trying to turn me on, and I'm not getting tuned on. This is a normal example a woman comfortable with being topless in a non-sexual situation, and a man, used to seeing that woman topless, not having a strong reaction to it. This is how all men, regardless of sexual orientation, would see breasts if women were as comfortable not wearing a shirt around men as my wife is around me. If my wife were to start teasing me and trying to turn me on, I would start getting horny, because that's the appropriate time for a person to have a sexual response to another person's body.