REDEFINING THE ISSUE

And the number one secular* argument against the coalition's plan to allow civil marriage in the UK;
We mustn't allow gays to redefine marriage.
?
How?
How do two adults who just happen to be of the same gender making a commitment to one another in front of their friends and family redefine marriage?
I know the classic term, according to the Oxford English Dictionary, is the union of a man and a woman, but well, how many people use (or even think of) the classic terms for wallpaper, sweep and physician?
That is, words evolve, but not in a Darwinian way, more of a Lamarckian way, that is, they alter to fit in with their surroundings and then pass that meaning to the next generation.
If the meaning of marriage is expanded to cover any type of consenting adult couple, then humanity will settle in with it, just like when they talk about a corner they don't mean someone who represents the crown in criminal proceedings, rather like a barrister today.

(Note : I have purposefully avoided taking the well worn defence paths of, 'how will redefining marriage effect your marriage?' And, 'just because same sex marriage is legal doesn't mean you will have to get divorced'. Because not only have those paths been worn down so nothing fresh grows on them, that technically isn't what is meant by those who claim 'same sex marriage will redefine the meaning of marriage').

*Yes, secular. Because you don't have to be a theist to think that those disgusting poofs shouldn't be allowed to mix with decent people.