What makes a person Gay is not basically his/her sexual orientation but his/her affectional orientation! The distinction between sexual orientation and affectional orientation is crucial to underscore to all people, particularly potential Straight allies of whom there are many.
When I was teaching in the university, when dealing with this subject, I would ask my class what is the first thing that came into their minds when I said two different words. I would say "Heterosexual," and the words that they said were such words as "marriage," "family," and "children."
I would then say the word "Gay," and almost everyone said, "Sex." Many people, when they think of Gay people think primarily of sex and sexual activities in which many Gay people engage. It's relatively rare in my experience to have people first think of sex when, for example, a heterosexual couple get married, or when a Straight person is characterized.
I suggest that the term, "Sexual orientation" may be retarding the Gay Civil Rights movement, and it might be far better to discard that term in favor of "Affectional Orientation." Of course, sexual orientation is part and parcel of what make us Gay or Straight, but it is primarily the affectional orientation that we possess that ultimately define us as one or the other.
Being Gay, just like being Straight, is primarily about love! It's about our emotional connection to people of the same or opposite sex respectively!
And why shouldn't we categorize and refer to people, when appropriate, by one's affectional orientation when dealing with Gay and Straight people? It is far more accurate a description of Gay and Straight people than is the emphasis upon sex and sexual activity that seems to currently falsely embody the public's major perception and defining of Gay people as distinct from their major perception and defining of Straight people.