I personally see no issue with the Civil partnership, but to call it marriage is incorrect. If you want to avoid pissing off a lot of Christians, which would be necessary for the sake of a quiet existence, don't bring their name for the ceremony into it. A marriage is a marriage, no matter what you call it, a rose by any other name would smell as sweet. But stop trying to plug this stupid 'gay marriage' ideal and just relent and call it a Civil Partnership.
Personally I don't care what it's called, but there are an obscene number of people, people of all faiths, in this world that will see this as a high-jacking of their special religious ceremony and if those who strive for homosexual equality rise to this and get involved in a flame-war then it just proves that we can be just as petty as they are.
Marriage is just a word, it's the sentiment behind it that matters.