- The unfairness of denying gay couples the right to marriage is like the unfairness of denying dogs the right to vote.
- The unfairness of denying gay couples the right to marriage is like the unfairness of denying men the ability to have an aborition.
If one actually considers the structure and mappings in these analogies, they make no sense. Still, it's likely that they are rhetorically powerful. Why is that? First, let's look at the structure of the analogies. The structure of the first analogy seems to be something like this:
Base: "Only humans can vote. Dogs are not humans. Therefore dogs cannot vote, and this is not unfair."
Is analogous to:
Target: "Only straight people can marry. Gay people are not straight. Therefore, gay people cannot marry."
The inference we're supposed to make from the Base to the Target is that the situation in the Target is not unfair, either, because the fairness of the Base and Target follow from the same set of relations. Obviously it's not true that the relations in the two domains are even remotely analogous except at the most abstract level. Gay people can marry. However, they can't marry members of the same sex. Dogs, on the other hand, can't vote for humans but not dogs. Furthermore, the difference in sexual orientation is hardly analogous to the difference in species. They are entirely different types of relations.
The second analogy doesn't fair any better. Obviously, gay couples are not biologically incapable of marrying, as men are biologically incapable of having an abortion. What is the real point of Burgess-Jackson's analogies, then? To compare the fairness of denying gay's the right to marriage to cases in which it would be absurd to call something unfair. The only premise required for making these comparisons is the one that they are trying to prove, namely that "Only straight people can marry, therefore denying gay people the right to marry is not unfair." While neither analogy presents a rational argument for Burgess-Jackson's position, because they presuppose that position and the analogies don't hold, simply making the comparison to absurd cases allows people to make the inference that calling anti-gay marriage laws unfair is absurd as well. Now that's good framing.