I apologize in advance for the length. But you asked for logic. And logic doesn't fit into a sound bite."What's in a name? That which we call a rose
By any other name would smell as sweet."
A word has no intrinsic meaning. It's meaning is only that which has been applied to it by society. "Marriage" is, of course, no different. That specific word appears to date back to the 14th century. For over 700 years, it has meant the union, specifically, of a male and a female. Over that time, implications of exclusivity have shifted back and forth, but the requirement of opposite sexes has not.
The societal meanings attached to the word "marriage" have thus been built up over the better part of a millennium. And those meanings were themselves built upon the existing meanings associated with the even older word that "marriage" replaced. Numerous traditions are based on those ancient societal meanings.
Those traditions weren't built on the concept of homosexual relationships. As such, to describe two homosexuals as being "married" is not an issue of rights, but an issue of definition. It requires a different meaning to be applied to an existing word. When the definition changes, the associated traditions fade away.
To the point, the stated objective of any attempt to redefine the word "marriage" to include homosexual relationships, is to gain for said relationships the sociopolitical status provided by all those centuries of tradition. But the traditions aren't based on the word. They're based on the societal meanings associated with it. By redefining the word, those societal meanings are also changed. And with different meanings come different traditions, and a different aura of sociopolitical status. As such, homosexual relationships will not achieve the same status as traditional marriage, but the new status associated with the newly redefined word.
Thus, ultimately, the entire concept of redefinition is self defeating. Unless the actual objective is to remove from those who meet it's existing definition, the traditions associated with the word. Frankly, I don't think that is the objective of most people trying to redefine "marriage." But, as any new definition will not rest upon those centuries of tradition, it's the only logical outcome. The complete transference of the old cultural meanings to the new definition is simply not possible, as long as society recognizes any distinction between homosexuality and heterosexuality. And, as a species entirely dependent on heterosexual reproduction, that loss of distinction is all but inconceivable.
The likely outcome is that society at large will simply create a new word or phrase to replace the redefined word "marriage." "Traditional marriage" appears to the current front runner. That new word (or phrase) will acquire the traditions and meanings currently associated with the old word, while "marriage" will take on new ones. In the process, the forced alteration of vocabulary will instill some level of resentment among those who must find new words to express old meanings. That resentment is likely to trigger a backlash against those who forced the change. Such a backlash is likely to reach a level sufficient to reapply the current societal meanings of "homosexual relationship" to the newly redefined "marriage."
As a case in point, a brief survey of American history will show repeated changes in the words used to describe black people. None of those word changes has in themselves, altered the sociopolitical status of black people, because the traditions stay with the meaning, not the word. The only way to remove those traditions would be to remove the distinction between black and white, a feat no one has yet achieved. But that elimination of distinction is, in theory, possible. Selective breeding could, again, in theory, completely destroy all bases for said distinction.
But no theory exists for removing the basis of distinction between heterosexual and homosexual. Our species simply can't reproduce without that distinction. So the path to applying the current traditions of "marriage" to homosexual couples is considerably harder than the struggle black people have faced. As such, and in light of the complete failure of blacks and whites redefine away their distinctions, a different strategy seems necessary.
To continue the metaphor, look to president Obama. Whether the societal meanings associated with the phrase "black man" are true or not, is irrelevant. Any honest person would concede that those connotations tend to be negative. Obama didn't win by claiming a newer, better, definition of being black. He won by convincing the majority of society that he didn't represent the negative traditions associated with the words. Having done that, he's permanently altering the set of meanings associated with the phrase "black man." Whether those meanings are positive, negative, or neutral, in comparison to those associated with the phrase "white man," is for our heirs to decide. But the phrase (or word) used, remains irrelevant.
The same concept applies for whichever word is chosen to represent homosexual relationships. Whether that word is "marriage" or "clishnew," the societal meanings will be the same. But, as using the word "clishnew" will cause none of the resentment that would come from redefining the word "marriage," it seems like a more logical choice. The goal, then, becomes to instill the desired societal meanings into the new word. Unfortunately, as traditions are slow to accumulate, that process is likely to take many generations. But my personal feeling is that the process will be smoother if started from a clean slate, as opposed to the current attempt at altering an existing word.
So, who's with me? I'll gladly march along side anyone to support clishnew rights and status, equal to those of marriage. When do we start?
In the interest of full disclosure, I don't recognize any government's authority to sanction any marriage, regardless of it's meaning. As such, I see this argument as purely semantic, and having no place what so ever in legal discourse.