You are right. We need to look at history with clear eyes. Every single human being alive today is the descendant of people who utterly destroyed their rivals - but not if you start history a few centuries ago. We are all descendants of the survivors, the winners. The descendants of the losers were never born. Even if a culture has suffered recent losses, at some point their ancestors gained their territory by either out-competing or invading others.
Not long ago, I posted the "What Have the Romans Ever Done for Us?" scene from the Life of Brian, which nicely sums up the childishness of criticism of western culture. Sure, western culture has many issues, not least the rise of bland corporatism that has decimated creativity and the arts, driven by the kind of neurotic self-hatred that is being taught to university students.