Take a look at a beautiful woman. Take in her lines, curves, swells and valleys. What you feel, as a heterosexual male, is natural to you. In point of fact, you don't even think about how your body reacts. If you attempt, instead, to apply such scrutiny to a rugged, handsome man, do you feel the same way? Do you control how you feel, when trying to examine another man in a sexual manner? Or do you instead feel indifference, perhaps even revulsion? Lord knows, I've tried. It'd make life simpler, if I could shift that basic, biological interest to what is viewed as normal, but the body seldom obeys the mind when it comes to attraction and intimacy. Your basest of physiological reactions are not something to change and manipulate at your slightest whim.
Consider the flavour you hate most. As time goes on, that may shift of its own accord, and you may find that what you refused to eat as a child appeals as an adult. But sitting in a locked room with a mountain of turnips will never succeed in making me enjoy them via brute force, nor do I apply a choice in my distaste for them. The same can be said for most stimuli that one can partake of - you don't decide what music you like, rather you find that there is music that you like. The difference is subtle but important. I did not decide that women are preferable, but rather found that in a world of two physical genders, one triggers interest and the other indifference. It is no more a choice than my utter hatred of country & western.
It is offensive to imply that I am abnormal by choice, as it is to say that I am simply being difficult out of a stubborn dedication to rebel. It devalues my interests by stating that they can be changed if I felt inclined to cooperate, and that the simple, taken for granted act of being who I am means less than it would we're it integral and critical to my being, rather than a decision. It gives ammunition to the religious zealots, so as to passively enable them to cry out of my deviltry and the immortality of my choices, when no choice has been made beyond refusing to lie to others and myself. It empowers lawmakers to draft against me, since catering to people who are simply choosing to demand equality is ever so much less important than protecting people who aren't simply wasting everyone's time with their inconveniencing lifestyles.
Perhaps an argument could be made to say that offense is the wrong term. But judging it to be a choice is certainly wrong.
