I'm not exactly sure that I derived anything supporting that statement from your link...
"On the basis of a 14th-century account by the Genoese Gabriele de’ Mussi, the Black Death is widely believed to have reached Europe from the Crimea as the result of a biological warfare attack." - the CDC website. The full story is that some plague corpses were catapulted into the Affluent port city of Caffa. Because the rich do not like being seiged, and they also owned boats, they fled to the homes of their friends all across Europe, rapidly spreading the disease across Europe.
"In the Early Modern period (1340-1500,) Europe experienced the worst human disaster in its history when the Black Death (also known as the bubonic plague) hit in 1347, destroying a third of the population. It is commonly believed that society subsequently became more violent as the mass mortality rate cheapened life and thus increased warfare, crime, popular revolt, waves of flagellants, and persecution" - from wikipedia. Now, I'm focusing only on Europe because the Horde can only be said to be responsible for the spread of the European black death (it was already raging in Asia at that time).
Hiroshima is, as far as I know, the most lethal atomic bombing in history, and it only killed 166,000 people at maximum (again, this is from wikipedia, because it's something we all should have already learned in school at some point, and thus shouldn't be subject to radical doubt)