Sandefur has an excellent refutation of Thomas Krannawitter’s bizarre analogy between homosexuality and slavery. Claremont is at its most bizarre when discussing homosexuality in particular and generally at its weakest (in terms of making coherent arguments, consistent with the enlightenment liberalism in which they purport to operate) when it discusses social issues in general.
Let me make an observation regarding argumentation and using extreme examples like slavery, something I’ve noticed while debating various issues over the past few years: When we bring up examples and comparisions, we may be doing it in two different ways: 1) we may be making an equivalence between the two things that we are discussing; or 2) we may simply be trying to demonstrate that we can’t rely on principle X to support policy Y, because principle X can be used to support the unsupportable policy Z. And often what it is that we are criticizing—policy Y—is in no way equivalent to the unsupportable example—policy Z. For instance, let’s say that the majority of people support “gun control” (our policy Y). That "the majority of the people support it" is our principle X. We could argue, well, a majority of the population supported slavery (our unsupportable policy Z). That’s a fair point.
We are not drawing an equivalence between slavery and gun control, rather, we are simply saying, that the majority supports Y cannot justify Y as a moral or desirable policy because the REASON we are offering in support of Y could also support slavery. It's the REASON of "the majority supports it" that we are truly criticizing, not necessarily the underlying policy.
Or take tradition. Slavery has been vetted not just by longstanding tradition in this culture, but practically all cultures around the world. What should that tell us? Tradition, even universal cross cultural tradition, in and of itself cannot justify anything (which is NOT to say that tradition has no value in and of itself, just that it cannot justify anything). So the proponents of same-sex marriage are often confronted with the argument: Cross-cultural tradition has always found marriage to be male and female (but because the practice of polygamy is so widespread, cross cultural tradition has NOT always defined it as one man/ one woman). So it’s a fair argument for proponents of same-sex marriage to note, “slavery was once justified by tradition, therefore the tradition of barring same-sex marriage does not justify that bar.” Again, this is NOT to make an equivalence between the bar on same-sex marriage and the practice slavery, but rather to point out that because tradition vetted slavery, tradition in and of itself cannot be used to justify a position against or in favor of Y, no matter what Y is.
Now even in lieu of what I’ve just written, when confronted with such an extreme example as slavery, it strikes many of us as if an equivalence were being made anyway, even though that's not what was intended. Try using such an example in your next argument and I'll bet over one-half of your respondents will take umbrage acting as though you have made an equivalence between slavery and Y, even when that was clearly not intended.
Now back to Claremont: The problem there is that they clearly DO make an equivalence between slavery and homosexuality. That’s what’s so bizarre about Krannawitter’s and ultimately Harry V. Jaffa’s argument that homosexuality is immoral. Here is Jaffa on this point:
What Mohr says here about morality being independent of opinion is common ground between us. He and I agree that "slavery would be wrong even if nearly everyone liked it." What he fails to see is that homosexuality is equally wrong [my italics]— no matter how many say they like it. Slavery is against nature, because it treats human beings like subhuman chattel. Sodomy is against nature, since it treats men as if they were women.
Later I will have more to say on Jaffa’s erroneous naturalistic conclusions—but right off the bat, any view that sees homosexuality as morally equivalent to the practice of slavery should strike us all as self-evidently absurd.