It's all a politcal ploy, to gain their desired goal of eliminating any moral restraint in society, so they can be free to publicly do whatever it is they want to do, and gain new, young recruits. Lesbians generally don't like "marriage" since it smacks of male domination, and male homosexuals are generally so wildly promiscuous that the whole "marriage" push is a transparent farce. They want to gain the sympathy of ill-informed people ("oh, the poor gays, they can't get married") and force the rest of the world into submission before their will.
Homosexual activists want domination, not tolerance. They are the most intolerant, domineering, fascistic group in existence. They want to eliminate the age of consent (or at least lower it to 12), legally force everyone to accomodate their weird practices, and legally prevent anyone from ever criticizing them and their goals. They will not stop until they are soundly defeated. Giving in to them will only increase their power (as we have witnessed in the last couple of decades). Capitulation will destroy society.