Is it just me, or did that article make absolutely no sense?

The way I read it:

First premise: an analogy can be drawn between the IP doctrine of "tarnishment" and the notion that gay marriage demeans traditional straight marriage.

Second premise: but the analogy is not appropriate, because the IP doctrine is designed to protect something entirely different than what the anti-gay marriage folks are supposedly trying to protect.

Conclusion: Therefore, the anti-gay marriage people are wrong to think that gay marriage will demean traditional marriage.

Shouldn't the conclusion be "therefore, the IP analogy doesn't really fit, and I should move onto some other argument?" I mean, because the IP concept isn't appropriate doesn't at all mean that there are not valid reasons for the traditional marriage folks to believe gay marriage demeans their institution.

I'm a huge advocate of gay marriage, but found this piece entirely unpersuasive.

Yes, it's unpersuasive. If it doesn't make sense to you, a supporter of gay marriage, then how is it supposed to convince an opponent?

Here's my arugment--if you really want to help protect marriage: Make divorce a felony.

what does it matter if gays want to get married? what are they, like 14% of the population, and maybe 25% of them want to get married?

divorce affects over half of all marriage. until you are willing to ban divorce--you really are lying about protecting marriage.

I think that you may have misread Mr. Yoshino's argument. The layout of the article wasn't to claim that an analogy could be made about gay marraige "demeaning" the institution to tarnishment claims in IP law, then show how this was a false analogy because "the IP doctrine is designed to protect something entirely different than what the anti-gay marriage folks are supposedly trying to protect." I agree - that would have been a thoroughly unpersuasive strawman argument.

As I read it, he used the analogy of tarnishment to show why the idea of "demeaning the institution of marraige" isn't a valid complaint - which is not because marraige is a different type of deal than a corporate brand name (though obviously it is) but for more substantive reasons. First, he argues that marraige isn't the intellectual property of any one individual. This is a deeper argument than just "they're different types of goods so it's a false analogy" - what he's saying is no one (and no group) has a right to claim they're defending marraige because marraige isn't theirs to defend. While historically only straight people have had access to marraige, that doesn't make it their institution to expand or restrict as they desire, and they can't legitimately claim to be harmed if marraige is "tarnished". To use his example, Hasbro can make a tarnishment claim if a porn site calls itself Candyland, but I can't as an owner and player of the game, because it's not my property to defend.

His second point is a more obvious one, just put in new terms to fit his analogy: that even if marraige were people's to "defend", the case that it's being "tarnished" or "demeaned" only makes sense if gay marraige is something that really is demeaning. Obviously, everyone who frames gay marraige as an attack on the institution assumes that it is, but he's just pointing out that the tarnishment argument only makes sense if you buy the implicit homophobia.