Humans love to DEHUMANIZED others. It's a necessary step to slaughtering them. Our brain architecture makes it inevitable, yes, inevitable. In good times we're fine. On a bad day, we massacre em all, they are after all, vermin, dogs, rats, swine.
Well, here is the answer in Less Than Human, Why We Demean, Enslave, and Exterminate Others by David L. Smith, Ph.d.
There will be a quiz. You can take it to find out if you are really a little
George Wallace (racist),
Mel Gibson (anti-Semite),
Joe McCarthy (anticommunist),
Ted Bundy (misogynist),
Jan Brewer (anti-immigrant)
J. Edgar Hoover (homophobe, racist and anticommunist)
or just Rush Limbaugh (dumb-ass.)