Homosexuality is the latest in a trend of hot-button issues in the church which can cause congregations to break up. It is not very difficult to infer why this subject inspires such passion, resulting in division.
I was pondering recently why some differences of opinion can cause division whereas others can be tolerated within a congregation. For example, I know that in my current church there are people who are pacifists and people who affirm the use of violence in defense of justice. It seems to me that the difference between these positions would be much harder to bear than a difference over homosexuality. The ethical implications of violence are huge for both sides, and neither side looks very good in the other's viewpoint. Yet for some reason, people from both groups (and everyone else) can get along in church. Why is that?
I think it has to do with the scope of church. It is easy to get along about violence, because the issue doesn't come up in the context of church. Since (ideally) the church is a place where no injustice is practiced, there is no opportunity to debate the issue. Homosexuality, especially as it pertains to the clergy and marriage, does travel through the church's space.
As a converse example, it is probably not very easy to agree about violence in the midst wartime occupation (see Bonhoeffer). So context seems to be all-important here.
This is purely descriptive. My observations cannot answer what differences churches ought to be able to bear. But I think it is important to take a look at what they can bear, and why.