Actually, you’re wrong. The Mongols slaughtered by the millions. And as far as religion, various religions slaughtered hundreds of thousands of people before Darwin and Hitler. Just in the religious wars of the 1600s hundreds of thousands were slaughtered. Try again.
Genghis Khan innovated many ways of organizing his army, dividing it into decimal subsections of arbans (10 people), zuuns (100), myangans (1000) and tumens (10,000). The Kheshig or the Imperial Guard was founded and divided into day (khorchin, torghuds) and night guards (khevtuul).[21] He rewarded those who had been loyal to him and placed them in high positions, placing them as heads of army units and households, even though many of his allies had been from very low-rank clans.[22] Compared to the units he gave to his loyal companions, those assigned to his own family members were quite few. He proclaimed a new law of the empire, Ikh Zasag or Yassa, and codified everything related to the everyday life and political affairs of the nomads at the time. He forbade the selling of women, theft of other's properties, fighting between the Mongols, and the hunting of animals during the breeding season.[22] He appointed his adopted brother Shigi-Khuthugh supreme judge (jarughachi), ordering him to keep records of the empire. In addition to laws regarding family, food and army, Genghis also decreed religious freedom and supported domestic and international trade. He exempted the poor and the clergy from taxation.[23] Thus, Muslims, Buddhists and Christians from Manchuria, North China, India and Persia joined Genghis Khan long before his foreign conquests. He also encouraged literacy, adopting the Uyghur script which would form the Uyghur-Mongolian script of the empire, and he ordered the Uyghur Tatatunga, who had previously served the khan of Naimans, to instruct his sons.[24]
http://en.wikipedia.org/wiki/Mongol_Empire
The Mongols only killed those who would not submit, and were largely indifferent to religion among their subjects. They did not kill simply because of who or what you were, as the Nazis did. Their violence was a tactic deployed to ensure control, not a means toward the end- extermination.
The religious wars of Europe lasted hundreds of years. No one can claim that anywhere near six million were killed in a single decade.