Why did European settlers call the native population of North America savages when they were the ones coming in and slaughtering the natives and taking their land?

Answer 1

Your question requires volumes by scholars to answer but I will provide some brief points.
The Europeans considered dark-skinned people to be less than human. Therefore they felt that since those people didn't live according to the customs of the white Europeans they weren't protected from exploitation.
In "New England" the English used a self serving philosophy to take the land from the native inhabitants. They decided that if the land was not enclosed (fences), and there were not inhabitations (villages and towns) and there were no tame cattle herds then the land was free for the taking. There were indeed settlements but not what the English viewed as proper towns. It was decreed the land belonged to King James I. He granted Royal Charters of vast tracts of land to English companies that came to exploit the land. Also, the native population was at an all time low because of deadly illnesses over the prior few decades in early America.

At first the native inhabitants welcomed the newcomers. The English companies had received royal grants of the land and they brought token payments of trinkets and supplies for the native population. The natives had no concept of privately owned land so didn't understand that the English were taking possession of the land as their private property by "purchasing" it with those trinkets.

Soon the troubles began when a few insightful native leaders realized what was happening. They were being starved and driven from their ancestral land. They became hunted and they retaliated. Slaughters from both sides ensued. However, not all natives waged war. Some continued to try to co-exist with the English. As English settlements multiplied and expanded inward those new English settlers wanted the natives removed altogether so they could settle ALL the land. The English decided the native population needed to be wiped out. The rest is history.

Many Americans have forgotten how that history began and view the "native savages" as the instigators and perpetrators. They have convinced themselves that America was purchased fairly from the native inhabitants.