I have to disagree. Sexual orientation IS a major part of a person whether they are gay, straight, bi etc. It is not however, a definitive explanation for someone's personality or existance as a whole but the fact still remains that alot of what we do as people, as sexual beings, in life, is driven by our sexual orientation.
On the other hand I don't think its necessary to constantly inform others of sexual orientation unless its truly relevant. It has became a social norm to constantly clarify sexual orientation and often being friends with gay people, defending gay rights or reading gay fiction, as a straight person, causes others to question your sexuality unless you clarify, which I personally don't so people assume i'm a lesbian.
One of my awkward gay friends said that to me today! Ha! (minus the 'mary' part of course)
So maybe society WILL reverse- "Don't look! Its disgusting! A GUY is holding hands with a GIRL! And in PUBLIC!"
But, ya know, I'm not gay.