…and keeping in mind that I’m speaking in general, not necessarily about the “gay marriage” thing (and further keeping in mind that I barely believe in straight marriage as it’s currently done, much less the gay variety), let’s try a little thought experiment.
The next time someone offends you, carry out an honor killing (whatever your ethnic background, it’s probably been part of your culture at some point in the near or distant past).
See how very much we do legislate morality. And pretty damn successfully.
Honor killing is an integral part of many cultures’ version of “morality” even today (and most cultures, if you go back far enough). Ours, recently (as in “within the past 100 years” in some parts of the country) decided it’s not any more. And they legislated it.
Ditto owning slaves, or having multiple spouses – although there’s no logical reason we won’t have the latter back within a generation.
That slogan “you can’t legislature morality” has always bugged me.