You're never letting go of your terrible analogy, eh? Just from a communication standpoint, you should try something else because you've been beating the mud drum over and over and it's still not making your point. The only value I've found in it is that the way you keep using it reminds me that water and earth used to be considered elements. Now we define elements as the atomic foundations of all matter. The meaning of the word changed because we learned new information.
The same is happening here. The meaning of marriage is changing because we now understand that two men or two women can also have a life-long relationship that is a family, can raise children, and be just as useful as members of a community as any other marriage unit.
Why does the biology aspect matter to the law?
Heck, why does it matter to you?
And I used to sound the civil union horn just as you are now, but the reality is that the word marriage is an established legal word. Changing it to anything else does one thing: makes idiots hate gay people more because they "ruined the word marriage for everyone".
Oh the outcries of the oppressed majority will be so loud! 'Wahhhhh! Those gay people made it so I can't get married! Now I have to join an union! Wahhhh!'
Marriage is the accepted word. It will not include gay couples under its purview. This is not a perversion of language, it is its evolution due to exanded understanding.
So again, to use your phrase: Tough shit, buddy. Gay couples have every right to be married, not some lesser or other thing. And they're not ruining anyone else's marriage in the process.