During the history of Christianity, a lot of people used Scriptures to define their theology? Does it mean all of them are correct?
No, but that's a part of the point.
Edit: I thought of something else that may help. Please note that I have not been arguing for or against homosexuality in this thread. My argument here is that it is not a good reason for a split as it is not an issue of core theology.
So let me provide an theoretical example without including homosexuality.
Consider that some Christians believe that sex without the purpose of bearing children is sinful and goes against God's will. Other Christians believe that as long as a couple is in a committed married relationship, they can be as intimate with each other as they please for no particular purpose.
Suppose the United Methodist Church had a social principle that did not condone sexual relations outside of a committed married relationship *and* outside of the purpose of bearing children. Many Methodists disagreed with this principle, but it's a social principle and didn't really affect them personally, so they just went on with things.
Then one day, a married couple believed they heard God calling them into ordained ministry as a clergy couple and started down the ministry track. Only problem was that the man had had an accident in the past and could no longer produce sperm and therefore had no capacity for having children. However, all signs pointed to them actively still practicing heterosexual sex.
The denomination got into a huge argument over it. People started taking sides. Both sides were adamant that their views were biblical and correct and that the other side was being either willfully sinful or willfully ignorant. The denomination started discussing the possibility of a split because neither side could agree on the purpose of marriage and if the denomination started ordaining people who were actively disobeying God's command to "go forth and multiply" then they were going to leave, and the other side was going to leave if they were forced into what they believed was a narrow-minded view of marriage, and unfair to those who could not bear children, did not have the capacity to raise children, or who were past their childbearing years.
Good reason for a split?