Isn't that what virtually every people group did? Look at what the Iroquois admit to being the "Dark Times" -- when the tribes fought each other before Columbus. And not just the Iroquois tribes. When they'd fight each other, kill each other, take over each other's land, and force the survivors to become part of the conquering tribe, which meant learning new customs.
Just like the white groups did to each other and other groups. Just like the Muslim groups did to each other and other groups. Just like the Asian groups did to each other and other groups. Just like the black groups did to each other and other groups.
Look at the climate graph in post 46. Know that most of the atrocities we fuss about occurred during the Little Ice Age, when everybody was struggling to survive. It's unfortunately too easy to justify taking over someone else's lands when your crop yields are low and you're starving. And when your rain patterns are less predictable. And when you're experiencing more deaths by plague. Such is life during the centuries-long cooling periods like the Little Ice Age (roughly AD 1300 to mid 1800's), or the Dark Age before that (roughly AD 300 to 900), or the Greek Dark before that (roughly 11th century BC to 3rd century BC, sometimes called the Era of Kings by us Bible geeks).
I'm not saying it's the only reason for those atrocities. But it's very much a factor. That includes the atrocity of my Anglo-Saxon ancestors forced out of modern day Germany during the Dark Age cooling period. (Call it the English version of a Trail of Tears. In fact, the word "Anglo" probably comes from the fact that they lived in Anglia in modern day Germany.) Many believe that the reason the Huns took over land west and south of them was because the Dark Age cooling period forced them to seek land that could grow crops. That displaced the Germanic Goth tribes and forced them to move into what was left of the Roman empire, taking it over by migration. The Huns kept coming and the Germanic Goth tribes had to keep moving, which forced out the Anglos, Saxons, and Jutes, pushing them north into the Denmark area. (Hint: forced north is bad during a cooling period if you're in the northern hemisphere.) They were starving out in that marsh land, so they crossed the channel into Britannia (some say the Huns were moving into the Denmark area and forced the Anglos out).
So the Anglo-Saxons ourselves are a displaced people.
So just because other groups did it in the past, it's okay that we did it in the late 19th and early 20th century, and should be given a pass for doing it? Being critical of the practice isn't allowed because everybody else in antiquity did it too?