Those who are opposing legalization of gay/lesbian unions don't know what they are doing. Why do I say that? The answer is simple. If gay/lesbian behavior is genetic, as many of them assert, when a person predisposed to gay behavior marries a person of the opposite sex and has children, his or her genes are passed on to another generation, thus multiplying the genetic disposition.
So if society demanded that all people of such disposition marry each other, and not people of the opposite sex, it would not take long for the gay/lesbian genetic disposition to disappear.