Our tastes are shaped by our own choices and actions. Taste in partners is no exception. We choose what music to listen to, what books to read, and what food to eat.
I disagree. And I'll give an example as a way of explaining myself.
I am a recovered alcoholic. And I was born with a genetic predisposition to become addicted to alcohol. I know this from personal experience, and from having discussed the subject many times with many other people, both alcoholic and not-alcoholic. My genetic predisposition manifests in the way my brain processes and 'experiences' alcohol. My brain experiences the effect of alcohol in my system as a kind of euphoria. I feel an intense sense of freedom, and creativity, and joy when I drink, and it begins with just one drink. And that sensation is so strong that it makes being sober pale in comparison. The first time I drank alcohol I got drunk because one drink made me feel really good, and my mind immediately presumed that a second drink would make me feel that much better. And it did. So I immediately fell in love with the idea and the feeing of being drunk. And from then on I wanted to do it again. And again and again.
Most other people's brains do not react to alcohol the way mine does, or does not react to it nearly as intensely as mine does. In fact, I have known several women over the years who couldn't get drunk at all, no matter how much alcohol they drink. For some reason, their brains simply did not process alcohol in the way most of the rest of our brains do.
You would say I had a choice whether or not to become an alcoholic. But I don't believe I had a choice. At the time I first began to drink, I was too young to understand or care about the consequences of what I was feeling and what I was doing in response to it. And by the time I was old enough to get some sense of the danger I was in, it was too late. I was already fully addicted. By the time I tried to stop drinking I couldn't stop, even for 24 hours.
We humans are not nearly as "in charge" of our thoughts and our feelings and our actions as we tent to imagine ourselves to be because much of who we are has been pre-programmed into us by our genetic histories, through the physical structures of our brains, and by our circumstantial histories and the concepts of reality that we have come to hold as a result of our experiences.
Some people engage in homosexual behavior because they want to, and they chose to. But many do so because they are inclined by their physical natures to do so. And they really don't have much, or sometimes even any, choice in it.
It was extremely difficult for me to stop drinking alcohol, and I have to avoid it completely, now, if I want to stay sober, healthy and alive. I cannot choose to have a drink or two and then stop like most other people can. One drink could very easily send me into an alcoholic binge that would last the rest of my life.
Until you have experience such a loss of self-control, it's difficult to appreciate how it can occur. But I assure you that it can and does occur, and it effects a great many different human behaviors, including sexual behavior.
Human nature is far more complex and powerful that I think you realize.