This issue is purely about Christians trying to force the law to make something that they don't approve of, for religious reasons, illegal for anyone regardless of their personal faith.

You're right that Christians are trying to produce a system of laws that align with their values. This is not wrong. That's all anyone is trying to do. However we come to our system of values, all anyone is trying to do is have those values reflected in the laws that govern the land. This has nothing to do with a separation of church and state. If the people of the U.S. decide that same-sex marriage should not be legal, then that is what the government should support, regardless of the rationale behind the sentament. Likwise, if the people decide that same-sex marriage should be legal, then again that is the choice of the government, regardless of the church.

Religion is involved because it drives many of the beliefs that produce laws, but that is hardly the same as saying the church is trying to control the government. The United States is supposed to be a nation where the people choose, and that means we get to choose with any rational that we want, be it faith or any other reason. Sure, the government could decide to throw out the will of the people in favor of "tolerence", "enlightment", "righteousness" or any other concept, but that wouldn't be the consistent with values this nation was founded on. It is the people who are "tolerant", "enlightened," "righteouss," etc. not the government.