We here in New York have been the latest to have to watch our legislators attempt to redefine marriage. They won't describe it as redefining marriage; they think they are merely allowing people with alternative lifestyles to be able to enjoy the privileges of marriage. But there are a couple of things they choose to ignore.
First of all our Creator has defined marriage as between a man and a woman and made us so that a man compliments a woman and she in turn completes a man. His Word very clearly establishes this parameter and says that those that don't follow these guidelines will not inherit the kingdom of God.
"But you yourselves wrong and defraud—even your own brothers! Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God." (To mention just one place)
The point here is that marriage is between a man and a woman and so a union between two people of the same sex is not marriage. It might be some sort of civil union that mimics marriage and it might be legal but is not marriage. To call it a marriage is to rebel against how God has defined it and suggests that somehow it is legit when it is not.
The other thing that the enemies of marriage remain eerily silent about is that once you say that there is no standard by which to define marriage except whatever society comes up with, then we open the doors to allow all sorts of unions with no ability to judge anything as wrong. This is already being seen in European countries where the pedophiles are using the same arguments as the homosexuals are using, that no one has a right to stop them from doing what they want to do.
So inevitably marriage must be accepted as a union between a man and several women or a woman and several men or a woman and her chihuahua or a man and his eight year old son. What disgusted society fifty years ago no longer does and little by little society becomes an immoral cesspool and it falls apart.
As Christians we need to be able to answer those who can't think beyond the next five minutes with biblical as well as logical arguments. Burying our heads in the sand or just calling someone a pervert isn't being ready to give an answer to the hope that is within us.