I mean if we're getting into it, "white man" basically genocided their whole population with disease. The Native Americans never did anything nearly so heinous.
I'm not sure I understand your comment. If the genocide happened due to diseases imported from the Old World, how is it "heinous"? It happened at a time where people had no clue what diseases and immune systems were.
But that happened in the 18th century though, by then of course, empirical observation had played its role and a few people tried to weaponize it. I'm pretty sure accidental contamination during the 2 preceding centuries had already caused a massive decline in population.
Whether or not they knew they were transporting disease at the time really doesn't excuse the end result: mass genocide. And of course this doesn't authorize taking land.
It totally excuses it. Intent is key. If you have no clue what a disease, a virus, an immune system are I don't see how you can be called "heinous" for unknowingly and unwillingly spread diseases.
As for lands, I don't know, lands all over the world have been changing hands since human beings learnt how to walk, most of the time after violence/war. It happened in 1500 when the concept of "nation" didn't even exist and the only way to say that a land was yours was to be able to keep it.
Well, then China is responsible for mass genocide due to Covid-19 then. After all, whether or not they knew they were transporting disease to other countries 6 months back really doesn't excuse the end result.