What a strange analogy. Evolution is a natural phenomena, while marriage is a state-regulated union. There is a set of reasons apart from tradition why legal marriage exists, and very little in that set would apply with any frequency to "gay marriage". The most obvious reason, of course, is that the division of labor between the sexes is inevitably derivative of the constraints created by pregnancy.
Brin doesn't really argue beyond this,
we see this fundamentally as an issue of equality.
But this is an error. It's an easy error to make.
You are claiming that this is the primary reason why we have state-regulated marriage? Two words: [citation needed].
UPDATE
@downvoter, if equality isn't a fuzzy premise, where is the line drawn between things that should and should not be equal?
For instance, why shouldn't everyone have an equal opportunity to participate in the Olympics? Why shouldn't everyone have an equal opportunity to be a CEO on Wall Street?
It's because they do not have the functionality that these positions require, as mynameishere pointed out regarding marriage. Claiming equality merely glosses over these important distinctions and does not bring any substance to the argument.
Sure, maybe same sex relationships can be artificially generative, but this is no where near the capability or likelihood to equal the basis for traditional marriage.
So, same sex relationships should not have the same benefits that are accrued by a generative relationship, since they do not require them and are thus just squandering resources.
Emotional issues are important, but they should not be the bottom line in a situation that clearly has a functional basis. However, the pro side seems to be mainly emotive in their driving arguments.
As a journalist (one who just finished interviewing someone I find personally despicable but who's done something newsworthy and interesting so merits coverage) I like to think that my readers are smart enough to suss out their own positions on the things I write about. It's not my job to decide which of the different views on a topic I cover is "correct" or "right." My job's to describe them and how they relate to one another and let the reader do his or her homework on which one they think is right.
Drew Curtis has a great chapter in his book in which he rails against the media's penchant for giving equal time to "crazy people." He makes a great argument, but the problem is that it comes from an assumption that your readers are too lazy and dumb to make up their own minds about an issue, so we should be selective in how we treat different sides of an argument. That doesn't sit well.
Right, but it's also not your job to draw false dichotomies and go out of your way to imply moral equivalence just so you can slather a patina of "fairness" over your work.
Even the best (especially the best?) journalists have to editorialize, whether they come to grips with that fact or not. The alternative would be to present an infinity of viewpoints on every topic one covers in any piece one writes. At some point one has to exercise discretion on what gets included and what doesn't, on what gets covered in detail and what doesn't. I don't think it's right or realistic to try to abdicate that part of one's journalistic responsibility.
Dedicating half of your story to, for instance, a crazy windbag representing a tiny minority for the (professionally misguided and misinterpreted) purpose of an unbiased piece is where the insanity comes in. If in researching a story you find that there are some dissenting views, you include a quote from them somewhere in the piece, but you don't turn your piece into that one guy or one group versus the original focus of the story. That's sloppy and misrepresenting the issue because you've mistaken "unbiased reporting" with "50/50 equal time for two views."
This also sets a dangerous precedent if those who present the arguments are convinced they know which one is right. If it is legitimate for them to favor one over the other, then they end up dictating what is "right" for the masses, which is essentially censorship.
A way to try & look at it from a position where you see something as this as an undeniable truth is to imagine a debate in a different time or place. Equal voting rights for women/minorities was once controversial in the US & Europe, How HIV infection occurs is controversial in some places currently. Would you be able to give equal time to all positions in these cases?