How people can take a moron like Santorum seriously boggles the mind. His chief argument is that the words "right to privacy" do not appear in the Constitution, but neither does "the right to breathe". Of course, we can INFER that the "right to breathe" is assumed under the Constitution, since it would be impossible to exercise any of our other rights without it. A similar INFERENCE is used to establish that we DO have a "right to privacy", given that the Constitution says citizens have a right to be "secure in their persons, houses, papers, and effects, against unreasonable searches and seizures".
EVILgelical Christian extremists hate the notion that people have a right to privacy because then they might look at porn or engage in wild sex parties or want things like birth control and abortion. Indeed, on this last point, Roe v Wade concludes that abortion should be legal on the basis of a woman's "right to privacy". How can people be "secure in their persons" if there is an intruder growing inside their bodies, threatening their health and even their lives. Therefore, necessarily, religious extremists have to be against the "right to privacy", so that they can continue to be endorsed by the freedom-hating anti-birth control movement.
Over on planet Dumbshit, where Ricky Retardo lives instead of planet Earth, Santorum argues that "If the Supreme Court says that you have the right to consensual sex within your home, then you have the right to bigamy, you have the right to polygamy..." Indeed this makes NO SENSE whatsoever, but what did you expect. The right to consensual sex does not imply the right to marriage. If it did then Gay people would not need separate laws to GET MARRIED. Having sex with multiple partners is not the same as polygamy, which is formal legal marriage to all these partners. Retardo also throws in incest and adultery, for good measure, but the major problem with incest is that it is almost never consensual and adultery is not against federal law. If it were then they could have attempted to prosecute Bill Clinton for "adultery" instead of just trying to say that he lied about it under oath.
He also makes the claim based on personal ignorance that, "In every society, the definition of marriage has not ever to my knowledge included homosexuality". Perhaps he does not know better, but even if no other society has yet acknowledged something that would still not be a good argument against it. There are plenty of things that no other society in human history has ever done, like walking on the Moon. That would not be a good argument that we should never do it. Someone always has to be first.
The fact is, however, that pretty much every society that ever existed has acknowledged and admitted that homosexuals do exist, and many of them, outside the Judeo-Christian-Islamic tradition, did not have serious problems with it. On the other hand, polygamy isn't all that big a problem because most men don't want to have multiple women telling them what to do all the time, and most women don't want to have only 1/10 of a husband who comes around once every couple weeks for a slam-bam-thank-you-maam.
However, if people do want to repeal polygamy laws or recognize gay marriage, it's still not clear how this consensual activity hurts anything except the religous prejudices of people like Retarded Ricky.