The definition of "preference" is: "A greater liking for one alternative over another or others."
When it comes to being gay, using the term "sexual preference" suggests to me that I've been with both men and women, and I prefer to be with men. In actual fact, I've never been with women because I have no interest in them in that way. Thus, no choice was ever made; I had no basis of comparison to make the choice.
I'm surprised when the term sexual preference is still used today. We know now that people are born gay; they aren't born straight and decide, based on their sexual experiences with both genders, to be gay.
So let's get the terminology right. Let's use "sexual orientation." Then I won't get my back up when it's implied that I chose to be with men, and that I'm less deserving of my rights as a human being because of it.