Some Christians make mistakes. Just because we believe in God doesn't mean we are perfect. But I can GARANTEE you, that a Christian who gets a divorce knows exactly what they are doing.
In this day-and-age, sometimes Christians will get a 'divorce' for financial rights, but they must not enter another relationship. Because in the eyes of God, they are bound together until death. But sometimes people need to protect their financial security and getting a 'divorce' might be the only way. But to a Christian, it is just a piece of paper.....
There is also such a thing as an enolment which under special circumstances is granted, and if you have one, only then can you re-marry.
As for the 'gay' part of the question: we do not support gay marriages because God has said that homosexuality is one of the darkest mortal sins. He burned down two cities for it, even after he gave them so many chances to change. We do not hate people who are homosexual, we just do not support their choices to act upon it, or to acknowledge their feelings as being right. It is true, some people are born with it - an in-hormonal balance and are gay as a result, but if they understand that what they feel is wrong, we do not spite them.