This redefinition of words business: the churches that have suddenly taken a keen interest in preserving our language as well as our sexual purity seem to have forgotten that word usage develops all the time. Have a look through the OED - there aren't many words whose meanings haven't changed over time. The causes of these changes are usually lost in time but we can often pinpoint them to new technologies or changes in social mores. For centuries 'computer' meant 'a person who makes calculations or computations' and it wasn't used in its current meaning of 'a device or machine for performing or facilitating calculation' until the 1860s. I guess recently published dictionaries have to include an endless list of new functions now. Words stretch to encompass the needs of the community of speakers. Did we redefine the words 'vote' or 'democracy' when women were finally enfranchised after a democratic history going back to antiquity that only extended the vote to powerful men? Of course not - we just agreed as a society that the thing that the word represented would now have a broader scope because we made a political decision to advance equality.
Religious understandings of marriage have tended to exclude gay people but the practice has changed dramatically over time. Plenty of examples of polygamy in the OT but we're now fixating on the 'man and the woman' bit of the 'timeless' definition rather than the 'two people' part which is far from eternal. The other thing I want to say about language is that, as all minorities with a history of persecution know, it is deadly in its capacity to hurt. When people say 'there's no need to redefine marriage' - I want to ask who says? Clearly if you're happily married to a partner of the opposite sex you might not perceive a need. But how equal would you feel if you were excluded from using the one word that is most associated in our culture with lifelong loving commitment? When I got married I was moved by the history of the institution and particularly by the writing about marriage - both literary and religious, ancient and modern, that is part of my culture. For some gay people, it's hurtful to be made to feel foolish for wanting to share in that tradition. Shakespeare didn't write a sonnet that begins 'Let me not to the civil partnership of true minds / Admit impediments.' It wouldn't have scanned. Imagine if we said that any black person couldn't get married they had to get 'black-married' or some nonsense like that. The divisive use of language on this issue is very upsetting for some people - I'm really saddened by the lack of compassion I'm hearing from some people of faith on this issue. The 'there's no need' argument totally ignores the feelings of a large minority of people in our society.
We don't legislate to change the meanings of words, we just do it - that's really how language evolves. The thing is that for most of us that evolution has already happened. I've never received an invitation to a celebration of a 'civil partnership' but I've been lucky enough to be invited to a couple of weddings which happened to have same-sex protagonists. Most of us are already saying 'wedding' and 'marriage' to reflect the wishes of the people involved rather than a vocal religious minority who don't like it. The redefinition - if that's what you insist on calling it - has already happened. I passionately support religious freedom but I haven't seen any convincing evidence that the new legislation will endanger it in any way. It's not the business of the state to tell faith groups what to believe, practise or preach but neither is it the business of faith groups to tell the state what rights to grant its citizens - or to try to tell anyone how to use the English language.