Humans tend to group the world into Us, the people with whom one shares ethical relationships that involve trusting in some certain amount of give and take; and Them, the people and things with whom was does not.
We each individually configure our sense of this by working out who we are willing to trust. Depending on experience and training, people give or withhold trust based on race, creed, gender, age, nationality, mode of dress, accent in speech, or any of a wide range of affiliations. Trust may also be given or withheld according to circumstances. An antisemite may wish to hire a “smart Jew lawyer,” and a white nationalist may feel that Hispanics or Blacks do fine as cannon fodder–“at least the good ones.”
A standard con when manipulating large populations is to play off of misconceived and inauthentic differences to “divide and conquer.”
This is easy to spot with regard to the traditional racisms. But it is just as present when passing a beggar on the freeway offramp who is “not my problem.” or turning away a refugee whose difficulties “I did not cause.” The judgment in both cases involves identifying the victims as “not my people,” in some way, and hence one of “them.”