I bet everyone knows or has seen at least one person who behaves/behaved in this manner.

atavistic (at·a·vis·tic): / at uh VIS tik /
adjective

(1) relating to or displaying a characteristic in an organism that has been absent for several generations, normally caused by a chance recombination of a pair of inherited recessive genes; of or relating to genetic recurrence, reappearance, or reversion
(2) exhibiting atavism; demonstrating ancestral resemblance; of or relating to being a throwback; resembling a more primitive form, as in atavistic architecture or clothing
(3) instinctive; uncivilized; manifesting primitive behavior considered long since suppressed by society

[From ‘atavism.’  Via French atavisme from Latin atavus meaning “ancestor” (literally “beyond a grandfather”), from Latin atta (“father”) + avus (“grandfather”).]

Usage: Racism of any kind is atavistic behavior that should be discouraged.