Since I'm not a Christian, I can't respond to that part of the question. I do believe, however, that it should be legal for same-sex couples to marry. Too often the family has not acceptedt the sexual orientation of the person in question, and when it comes to how they wished to be taken care of at the end it is ignored, and so is the long term partner. If they were legally married, then the partner would have all of the rights of any other spouse. I believe everyone has the right to live in a way that gives them happiness, and the current laws deny this option to same-sex partners. JMO.
Btw, I do agree that Christianity is supposed to be a religion of tolerance, acceptance of others, and loving others for who they are, so to me, a good Christian would vote for this. Sadly, many consider that it is morally wrong by their standards, and wouldn't. I ask them...who gave anyone on Earth the right to judge others? If I have not walked a mile, or even a step, in someone's shoes, I have no right to judge them, even if I have walked in similar shoes.