When it comes down to Us versus Them, never side with Them. That's true for all people, and all situations. Just ask Fredo.
Now the trick to peace and unity is to make sure you never box people into a corner where all that's left to them is that stark line in the sand.
You have to keep the process open and keep it from getting that far, so that people are free to act for the common good, not just their own interest.