Of course it was justified. The people of the Americas were for the most part barbaric. Their lives were nomadic, living off the land, warring with other tribes and dying before they were 30.
For those who think living off of the land sounds great, watch the Survivor shows. It was often very cold, or very hot, food was scarce or abundant depending on the cycle.
Very little agriculture was going on in most tribes, so they followed the herds of wild animals and ate what grew naturally.
These people hadn’t even invented the wheel, and had eaten horses into extinction. The Spanish reintroduced horses to America, and the plains Indians finally had a mode of transportation.
Without transportation and agriculture, the civilizations were already marked for extinction.
I haven’t heard a single Native American say they’d rather still be living in the stone age. Running around naked, making crude weapons out of rocks and sticks, sacrificing each other to their pagan gods, and living to a ripe old age of 25. What a life. Contrary to what they’ll usually say, America didn’t belong to Native Americans any more than it belonged to the rabbits who lived on it. They owned individual tribal lands separated by large swaths of no man’s land. There was not even a collective identity, being mostly at war with one another. They’re better off now, since they still own large reservations that are more like independent countries than anything else.