But that's the point of faith and personal beliefs - they are what people believe and have a right to believe. They don't have to be justified with literal or loose bible interpretations.
Broadly I can agree with you, tiggytape, but in this case the entire religious argument (at least as far as I have seen it) has been based on a couple of passages in the bible which prohibit the practice of homosexuality. It has not been an extensive argument put forward based on the teachings and example of Jesus, for example, or based on centuries of study into the true meaning of marriage, it's always just 'it says it in the Bible '. As a reason for denying the rights of other people, it seems lacking. When debating such matters with religious people I'm prepared to work within a framework of personal belief, but I rarely come across an issue which seems to be adopted so dogmatically (pun intended) and without a supporting explanation. This is purely based on my own experience, of course.
Personally I think those opposing this bill should insert the words 'mixed race' in place of 'same sex' and see if they still think they will be able to justify themselves in twenty years' time when gay marriage is as normal as interracial marriage is today. However, social change rarely happens after all parties are convinced by the need for it - so we can only hope and wait.