I'm just gong to put my response to OP into the thread. I'm not really sure if these points have already been brought up since I didn't read the entire thread, but here I go.
The issue here is not really whether gay marriages within christian churches is moral from a christian standpoint; We both seem to agree that it isn't. Case in point: Matthew 19:4-6
4 And He answered and said to them, “Have you not read that He who made them at the beginning ‘made them male and female,’ 5 and said, ‘For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh’? 6 So then, they are no longer two but one flesh. Therefore what God has joined together, let not man separate.”
Instead, the issue of debate is whether It should be legal at a federal level in the United States.
Looking at the way it was legalized, Judicial Review via Obergefell v. Hodges, It's pretty clear that this particular decision should not have happened. Besides it being a clear violation of states rights, It effectively attempted to silence debate on a very controversial issue.
How Controversial? Well, even the most conservative polls put the percentage of americans opposed to Obergefell v. Hodges at 35-60%. That is 112-200 MILLION People who's opinions have simply been disregarded as outdated and irrelevant. This is not democracy. This is fascist-style disregard for what your people want.
What's even worse is that this decision was not handed down by an elected body, such as State legislatures who had previously banned gay marriage in several states, or congress, an actual nationally elected body. Heck, it was not even given out by executive order via the President, another nationally elected official.
No, this decision was made by what amounts to an appointed aristocracy. This is simply inexcusable.