It can be a delusional symptom of psychotic disorders
By Alvin F. Poussaint
The psychiatric profession's primary index for diagnosing psychiatric symptoms, the Diagnostic and Statistical Manual of Mental Disorders (DSM), does not include racism, prejudice, or bigotry in its text or index. Therefore, there is currently no support for including extreme racism under any diagnostic category. This leads psychiatrists to think that it cannot and should not be treated in their patients.
To continue perceiving extreme racism as normative and not pathologic is to lend it legitimacy. Clearly, anyone who scapegoats a whole group of people and seeks to eliminate them to resolve his or her internal conflicts meets criteria for a delusional disorder, a major psychiatric illness.
Extreme racists' violence should be considered in the context of behavior described by Allport in The Nature of Prejudice. Allport's 5-point scale categorizes increasingly dangerous acts. It begins with verbal expression of antagonism, progresses to avoidance of members of disliked groups, then to active discrimination against them, to physical attack, and finally to extermination (lynchings, massacres, genocide). That fifth point on the scale, the acting out of extermination fantasies, is readily classifiable as delusional behavior.
Time after time we see how racists are unable to process information. You tell them their words and images are stereotypical and they deny it. Even though the stereotypes are obvious to an objective observer. Consider Chief Wahoo, for example.
We've seen how crazy people get about their Indian mascots. Their devotion is totally out of proportion to the mascot's minor role. It borders on religious fanaticism. People defend their mascot as if it's their child, their parent, or their god.
We see religious and racial fanaticism come together in Jack Chick's Crazy Wolf. Chick thinks Navajos are devil-worshipers because he can't conceive of a non-Christian religion. He's like some autistic child whose senses don't function properly. Show him a picture of Changing Woman, explain her un-Satanic story, and he'll cry, "Devil!"
For more on the subject, see Everybody Is Racist and Highlights of the US Report to the UN on Racism