Political affiliation
Religious conviction
Birds of a feather who flock together don't hate each other or massacre one another. Do they?
Of course within the political affiliation will be the very rich and the very poor but since they share the same political dedication to whomever/whatever they will perforce get along.
Same with the religious. Some are VERY VERY wealthy. Others are very very poor. Some are in the middle. But if they are all Methodists or Catholics or Presbyterians or Jewish or Quaker they won't hate one another or sabotage or undermine or war with their neighbors.
That's how you achieve WORLD PIECE/PEACE Mr. chump. Ya wanna go for the Nobel PIECE/PEACE prize? Restructure all neighborhoods so that all birds of a feather live together. What could it hurt? Everyone says so!
You have the power to do whatever ya wanna do. Wanna do that?