In witch case, policy, or situlation did the motto "kill the Indian, but save the man" play an important role in western expansion?

When the settlers and pioneers were under attack by the Indians. Kill the Indians who were at the moment behaving like animals and save the men under attack. It can also be applied to the idea that Indians were thought of as savages. So it may be suggesting to civilize the Indian's so they can be men who are not 'savage'.