Because, deep down, as with so many apparently mysterious aspects of the human condition, there is a consciousness of the - in this case, disgusting - truth. /2.
The fictional idea humans are divided into different races isn’t about skin colour, horrible and pervasive though grotesque behaviours in that context are. It’s about the dehumanisation of others. Literally. “Race” is a euphemism for “species”, regardless of skin pigmentation./3.
The deep motivation for what we call “racism” is the dispossession of others: “sub-humans”, or indeed “non-humans”. Dispossession of property, liberty and ultimately life. Why? For gain. /4.
The systematic violation, dispossession and massacring of those the Nazis defined as “Jews” - “white” skinned, of course - was justified by the killers and their helpers on the grounds of “Jews” being “sub-human”. Not really human. /6.
Its intended effect, of which genocide was an integral part, was exercise of sweeping power and massive theft of resources to benefit a particular group: ludicrously, again euphemistically, defined as “Aryans”. “Thieves, murderers and fellow travellers” would be more accurate./7.