History does not follow a linear path as you have described. Considering the the numerous atrocities committed by the British Empire throughout the world, including the genocide of Native Americans in what is now the eastern U.S., the genocide of Australian aborigines (including the extermination of the entire indigenous population of Tasmania), the engineering of man-made famines that killed tens of millions of Indians between the 18th and 20th centuries, the trans-Atlantic slave trade that saw millions of Africans shipped against their will to the Americas (many of whom died in the journey, and the rest to suffer many decades of oppression), the use of forced labour to build railroads across Africa, the illegal export of opium to China that caused tens of millions of Chinese to become impoverished addicts (thereby driving the country into the ground), and many other crimes, I don't think it is fair to say that the British were 'far more humane' than the Huns. The reason why the world is (relatively) more humane and peaceful today than in the Middle Ages is because we as a world are far more interconnected and interdependent, thus making international wars less attractive while at the same time increasing general awareness of cultural diversity and different kinds of people. Advances in technology have also played a huge role in creating a more humane world. As a species, however, we are still just Homo sapiens, possessing extraordinary powers of creation and even more extraordinary powers of destruction.