Let me get right to the bottom line. If the United Methodist Church is going to break in half we better do it for the right reason. LGBT equality is not it. We've disagreed on this ever since the word "homosexual" first made it into the Book of Discipline in 1972. I don't see any reason why we should split now more than 30 years after that fight began.
Biblical authority is not it. I'm working on a post now that shows how this is a strawman. Short version: We all agree that the Bible is authoritative. Our disagreement is about how the Bible is authoritative.
Use of the Quadrilateral is not it. We've misunderstood and misused it almost from the moment Outler started talking about it.
I'm convinced that the core problem in the UMC right now is one of identity. We don't know who we are. If you were to ask 100 United Methodists why they are United Methodists instead of, say, Lutherans, I bet you'd get at least 75 different answers. Adoption of a purpose statement helps, but when that statement is so broad that it can serve as a statement for any Christian church (at least I hope the Great Commission could be adopted by any Christian church) it doesn't help much. to be United Methodist should mean something besides simply being Christian. But what is it?
I don't agree with them on much, but the Confessing Movement is right - we need a confession of faith. We need a statement that says what is at the core of what Methodists believe. We need a method of adopting such a confession at General Conference by a supermajority (say, 75%) so that it is broad enough that no one group can control the content. It should be voted on line by line, point by point, so that no single issue causes a whole group to vote it down. It should be a very short confession, at least in my opinion, exemplifying Wesley's "Catholic Spirit". And it should be in the Constitution so that changing it after it is adopted is possible but extremely difficult.
If we adopt a confession and a group within the UMC can't sign off on it then we should split. Then we would be splitting for the right reason - because we have fundamental differences of opinion that prevent us from working together for the glory of God. I am fully convinced that we do not have such fundamental differences of opinion. We have a lot of loud voices that have stopped listening to each other and would rather be right than work towards solutions.