This is fantasy. Take the example of Rwanda. The two factions were the Tootsies and the Hutus which did not even exist before some colonial power told them so.
What happened next was genocide.
Take christianity. Why should a small country like Ireland, which is 'christian' be so divided.
I always thought to be 'christian' was to be tolerant.
Next examine Islamic countries.
Different flavours of Islam. Iran and Iraq.
Next Take the Balkans. If you examine history this was the border between the old empire(Ottoman) and the new (Austro Hungarian), met.
An update- a known Russian spy was eliminated in Britain, he ate sushi which contained Polonium( a radioctive substance). It was enough to make him suffer while his organs failed and endure a painfull death. It is reckoned to do this you have to be a Nobel prize winning scientist. The reasons why this happened are unclear, as Russia is no lomnger seen as an enemy of the west. Answers please.