This is referred to in The Twentieth Century Book of the Dead by two words: parathropization, and mechanthropization.

In the first one, the in-group defines some out-group (Jew, trans people, or even just "liberals") and non-human. In the second, great machines and systems are set up to actually implement the killing, such that most of the people involved don't even see the deaths.

Strongly recommended for you: https://www.amazon.com/20th-Century-Book-Dead-Controversial/dp/B000AXW7LC