Humans...like any surviving organism that relies on cooperation to survive...simply operate under a friend/enemy distinction. Ants are totally self sacrificing for their own colony but they attack any ant from a different colony on sight
The natural instinct of humans is similar but just less severe.
But in essence, we care less about evil being done to a rival tribe (hostis was the label in latin).
Individualist liberal philosophy has tried very much to obfuscate the fact that humans have tribal impulses at all...being philosophically incoherent if it accepts the existence of tribalism. We are supposed to believe that humanity is just one big tribe and the only conflict is between individuals.
But obviously stuff like blm riots or gerrymandering to avoid having too many black voters proves that this attitude is just naive.