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.
Some points:
The Yuan dynasty was a Chinese dynasty. "It's not a Chinese dynasty because it was ruled by Mongols" is a talking point pushed by Japanese, Korean, and Vietnamese ultranationalists as well as various Westerners.
The invasion of Japan by the Yuan dynasty was closer to 700 years ago.
The actual war that happened 500 years ago was when Japan invaded Korea in order to invade China. The Sino-Japanese Wars was just Japan attempting to use the same playbook they did half a millennia ago.
Ah, thanks; I actually don't know about the events, I was repeating what the guy who replied said.