That's patently not correct, mongols were this cartoonish evil that was killing left and right, for fun, murdered whole cities even when they surrendered without fight just because army leader didn't like something or slept badly last night.

Parallel with Hitler's conquest is not bad, a slightly different ideology but again "we above everybody else who are subhumans anyway so who cares", hence overall decimation of whole mankind (albeit the process was different, result was same).