For the mentality of that time, this was moral. Europeans grease the Indians as wild and profane. In this way, they considered it pertinent to invade and to explore the territories of the American continent and to impress its culture to the native inhabitants. This was called Eurocentrism.
Clearly I find this absurd, completely immoral. It is not right to invade a territory and exploit, enslave, and kill its inhabitants. Unfortunately this was done in a horrible way, but it is part of our story.