Violence is often normalized so long as those who are perpetuating it are politically aligned. For example, Mustafa Kemal Ataturk and his government genocided millions of Greeks and Armenians. Most nationalistic Turks found nothing wrong with that. In fact, Hitler admired Ataturk a lot, and used his actions as a template for his own programs.

"The minority problem in Anatolia was solved in a very simple fashion... “Only through the annihilation of the Greek and the Armenian tribes in Anatolia was the creation of a Turkish national state and the formation of an unflawed Turkish body of society within one state possible.”

Multiethnic nations don’t tend to last very long.