How did Europeans justify imperialism?

They justified it by saying the cultures and religions of the natives were wrong, in the ways of the Europeans and they would introduce them to Christianity and modern European culture

Americans justified imperialistic behavior by: Claiming that it was their responsibility. Americans and Europeans both claimed that it was their responsibility as superior races to uplift, civilize and Christianize native peoples. This was known as the White Mans Burden and was based upon the ideas of social Darwinism.