As others have said, I think it comes down to exposure in terms of removing the "ick" factor. A lot of things in the past were likely misunderstood and part of a more hidden/secretive community. So the simple lack of knowledge led people to believe it was odd, unusual, unhealthy, whatever. However with all the sexual information available today, so many more people are open to trying things because they're able to see it in a light other than "the unknown" or what have you.

However, I think there's a big difference between an increase in anal sex for example and the issues you brought up such as beastiality, scat, etc. That difference being health, physical and emotional. There is nothing wrong with anal sex, BDSM, etc, it's a person's choice whether they want to engage in those activities, but in most cases they are not harmful. Whereas bestiality, scat, etc are definently harmful to a person's body and mind.

Thank you for making my point for me. The Ick Factor is mobile. In West Virginia, the Ick Factor will not include first cousins (to continue the joke) but it would in Chicago. In parts of New Guinea, canibalism wouldn't make the list, but it will pretty much anywhere else. The Ick Factor is completely subjective and depends on the culture and experiences of the individual saying "ick".

Let's say that in early youth and adolence you hung around with a bookmobile-driving Chicken Fucker (to blatantly steal from South Park). If the only sexual outlet you ever saw involved a guy in a rainbow suit making sweet love to a chicken, well, you're probably going to grow up thinking fondly of the clucks of love. Sorry, I'm just trying to make a point. :)

Incest is a topic I hadn't thought of when I first posted. Freud would say (Civilization and its Discontents) - and this applies to some of these other topics as well - that the "ick factor" towards incest evolved over time for the stability of civilization. That said, I think immediate family is the only one that people are genetically predisposed to find repulsive. Socially, cousins have also filled into that category, but there are plenty of cultures in which relations with a cousin isn't totally unheard of. The idea of relations between a brother and sister is MUCH more rare.

Women, or if you're talking about FTM's, men.

Transsexuals don't alter their bodies for sexual purposes for the most part. A tiny minority do, but they're the exception. For the vast majority, It's about identity, changing her body to match who she feels herself to be inside. Many are asexual before transition or afterwards. It isn't about sex, it's about soul, about being true to who you are.

Gilda

Polygamy isn't a logical extension of same-sex marriage. That's a meme that's been promoted over and over again by opponents for so long that it's reached the point where people are beginning to accept it as true.

Removing sex as a required factor in determining who can marry whom doesn't logically extend to the removal of number or age or species or degree of familial relationship, all of which are seaparate issues deserving their own separate discussion and debate.

Gilda

I'm not sure I agree with that. The way I see it, at least, the base argument for homosexual marriage (which I support, btw, for this very reason) is that it is not the place of society to place boundaries on the validity of different types of love between consenting adults. In this way, allowing multiple partner marriages is a necessary extension of allowing homosexual marriages. Any other explanation for the legalization of homosexual marriage, IMO, is simply a compromise to appease those who would fear a departure from their own traditional values.