The maxim Lee Harris advocates, "Never let a good argument get the better of your common sense," appears to have been freshly minted for his TCS column on why conservatives should not succumb to the siren song of reason, evidence and good arguments, and should be proud to be as stupid as a Tory aristocrat. Harris's catchphrase reminded me of my concern about Judge Smith's use of "common sense" as a rational basis for denying same-sex marriage in Hernandez v. Robles, and a lengthy discussion over that phrase. It only now occurs to me that for conservatives, "common sense" is a genuinely legitimate defense against rational argument. As Einstein said, common sense is "the collection of prejudices acquired by age 18," and prejudice against homosexuals easily can be cloaked in it. A legislative assumption that same-sex couples are worse parents than opposite-sex couples thus avoids the Romer problem of appearing to be animus. This isn't bias, it's common sense!
Harris's explication of the Jewish prohibition on eating pork is fine until he concludes, 'So why not amend the prohibition on the eating on pork to read: "Thou shalt not eat pork unless it has been prepared according to the modern hygienic standards?"' From what I understand, modern Jews are well aware that one can eat pork without illness now; Yahweh's prohibition may have originated as a way to avoid trichinosis, but it is now part of Jewish identity. Harris doesn't seem to grasp that one can adhere to a tradition simply because it is meaningful to the individual. Thus the difference between the pork prohibition and the same-sex marriage prohibition: Jews do not try to ban others from eating pork, because they recognize pork avoidance is something peculiar to their (and Muslims') religious tradition. It is not something that belongs in secular law. In contrast, Harris and other opponents of same-sex marriage are not content to avoid it for themselves. They must put the prohibition into law and enforce it on others who do not adhere to their tradition.
This is the problem with using tradition as a rational basis for law. Traditions have their meaning through particularity: the Greek Orthodox's midnight Easter service, the Englishman's boiled pudding at Christmas, the African American's wedding jump over the broom. When tradition is given the force of law, particularly in a heterogeneous society, it must be justified with reason if it raises protests from some of those on whom it is enforced. And if those who uphold tradition say that they do not find the other side's arguments to be good -- for example, if Harris thinks that the law must make distinctions between the sexes, and therefore same-sex marriage prohibitions are legitimate -- then they should openly state that they disagree with the premises of those arguments. Hiding behind unreason, whether it is called tradition, common sense or "redneck wisdom," merely embitters one's opponents, who under Harris's prescription would literally go unheard. Stuffing one's ears with cotton is a good way to avoid sirens, but it is a very poor way to behave in a democratic polity.