native Americans were left very weak after pandemic of “European diseases” broke out in their communities, rendering them too weak to be enticed into hard labour.

It is most likely that none of the European colonialists around the world wanted to carry out massacre because it's impractical.

The Spanish and British colonialists wouldn't have brought in African slaves to America if they had massacred the natives purposely. The massive death of native Americans was due to infectious diseases unintentionally brought by the Europeans, not massacre by guns.

The theory that native Americans were extremely proud and could not be enslaved therefore the European colonialists had to massacre them is also not true. The historical fact is that native Americans were left very weak after pandemic of “European diseases” broke out in their communities, rendering them too weak to be enticed into hard labour.

The mass death of indigenous Americans and aboriginal Australians were NOT carried out by the European settlers/colonists intentionally.

Indigenous Americans and aboriginal Australians were struck by pandemic of germs and viruses brought by European settlers/colonists that they weren’t immune to. Some people claim that Europeans gave ‘flu blanket’ to the natives intentionally to kill them off, which is largely unfounded.

Unlike native Americans and Australians, Africans do have frequent contact with Europeans and Asians throughout history (war, trade, missions etc), hence they are more immune to Eurasian pathogens, and less fatal pandemic broke out in Africa.