As Graeber suggests, there may have been a distinctly European mode of imperialism which dates back to Rome - possibly earlier - and which has a consistently violent, self-justificatory, and abusive character.

I didn't see Graeber (in Debt, I presume) suggesting a peculiarly European mode of imperialism. He sees parallels between Europe and India's medieval structures after the end of the first age of empires ca. 300BC - 600AD. Of the three major civilizations born in the Axial Age (China, India, Mesopotamia), China seems to have had a different development, not having lost its empire in the "dark ages" of the late first millennium.

Maybe there was a lasting difference between West and East due to the difference between Alexander and Ashoka, but I don't remember that being one of Graeber's themes. I got more an impression that he argues that debts are one of the prime drivers of atrocity as heavily indebted people engage in high-stakes bets to try to get out from under heavy debts. He dwells on the Spanish conquistadors in the Americas, but he doesn't imply their behaviour is characteristically Western.

In the long run, we're all misquoted — not Keynes