Just as a possible counterpoint to this: Lebanon has been highly divided by sectarian conflicts, mainly between Christians and Muslims, but has managed to stay a cohesive state since its founding in the 40s.

Don't get me wrong, I wouldn't point to Lebanon as some beacon of stability or good governance. But despite decades of problems, including a long civil war, Lebanon's government and civilian population still exist without a major external power forcing them to stay as a single cohesive state.

If they can do that, maybe a one-state solution for Palestine and Israel isn't completely unworkable. If nothing else it sure seems like an improvement over the current situation.