Trying to understand my opponents

In the past couple of weeks, I've read rather extensively on what the formal position of the Mormon church is in regards to same sex marriage. They're hardly the only religious group out there who feel the way they do--the Catholics, for example, are really no better--but the Mormons were the funding source for the Yes on 8 campaign, and thus bear much of the brunt of the angry response.

Anger alone isn't terribly useful, though.

What really struck me is the pervasive idea that setting up two differently understood relationships described by the same word would undermine one of those relationships. A lot of people really seem to think that a couple down the street getting married would indeed affect their marriage if they don't think that the people down the street should be allowed to be married. The point strikes me as entirely nonsensical, and it's stated with an air of obviousness.

And then I realized that I state my view that whether or not I can marry a man in no way changes and heterosexual marriage with an equal air of obviousness. So it now seems that I need to explain that in more detail.

Let's pick a different familiar relationship; one that's a little less politically charged. I'm going with Brother, mostly because I have one of those.

Now when I say I have a brother, I mean that I have a male sibling a year older than me who has the same parents I do. We grew up in the same household, had many of the same teachers, many of the same friends, etc. We still talk most days, even though it's been years since we've lived together.

There are a lot of other forms of brothers, though. Among my extended relatives is one immediate family of a double second marriage. The father's first marriage resulted in a son. The mother's first marriage resulted in two sons and a daughter. The double second marriage resulted in two more sons. One of the five sons was adopted. Thus, their family involves males who are full genetic siblings, half genetic siblings, and adopted siblings. They're also all brothers, in a sense I agree with. Well, except for the daughter; she's a sister.

There are also people who use the term brother to mean people they've never lived with nor share any genetic link to. A number of religious organizations, for example, use it to refer to fellow believers who are male. Monks are traditionally referred to as Brothers. Fraternity members also typically refer to each other as brothers. I don't think any of these relationships actually fall under the heading of brotherhood--sharing neither genetic nor social parents means you're not really brothers in my book--but I recognize that others disagree with me here, and use the term regardless.

So, clearly there are a bunch of different relationships encompassed by the term brother, many of which mean entirely different things than my relationship with my brother. And not one of them changes or impinges on or threatens my relationship with my brother. He is still my brother, and the fact that other people use the term brother to mean someone I don't feel is actually their brother is completely irrelevant to that fact. If monks legally became brothers, it wouldn't threaten my relationship with my brother at all, nor would those of us from the males-who-share-parents crowd need a law designed to "protect" the institution of brotherhood. After all, brotherhood is traditionally a familial relationship, and we all know how the family unit is the central organization of our entire society.

Apply the same to sisters. Fathers, and Mothers, both of which can be religious titles as well as familial relationship. And that's just the nuclear family. Things get even more complicated and hazy when you look beyond those.

So if you're so certain that only one meaning of marriage can exist, only one exact specified form of the relationship, and that it will be undermined if anyone else ever uses the term...why does the same not apply to brotherhood?