Andrew is dead wrong.
The LDS Church supports these constitutional amendments to define marriage as being between a man and a woman because it believes that marriage is not just a word. Marriage is an eternal principle. A principle which modern day prophets have revealed to be strictly between a man and a woman (see The Family: A Proclamation to the World). In our view (and I know there are alternative views - I used to have one of them), defining it as anything else would be mocking God. And that is not something we(I) are prepared to do.