Sexual "preference" should be a protected right. That's what we're arguing and fighting and voting for. It's not an imbecile argument. As many studies show, sexual preference isn't a choice, at least not completely. At the absolute minimum it's 50% genetics and 50% early develpment (marty klein, America's war on Sex, an excellent book). So it's not different that race.
But even if it is, why do we get to decide who another person chooses to love? That doesn't sound like 'pursuit of happiness' to me