After what China did to Japan 500 years ago (under Mongol rule) (not Mongol rule as a hexbearer pointed out actually), they have no right to condemn Japan for anything; also bacteria, viruses, what's the difference? Also it was an attack, not an epidemic that formed naturally like they have throughout history.
Chairman Mao had a somehow positive view on Cao Cao somehow, he thought if Cao Cao somehow won earlier he could end the Three Kingdom period before it even started and subsequently less people would die.