That is highly unlikely given that I am biracial myself.
That is determined by a professional that is capable of doing a mental health status exam, forensic exam based on symptoms of a particular mental illness, and the ways in which the particular delusions interfere with natural thought processes. Someone who is delusional may be completely out of touch with reality, and therefore, unable to make decisions based on reality. They make decisions based on their delusional state.
No one person is responsible fully, but everyone bears a degree of responsibility, and those who are public figures, bear more responsibility for considering how their words may affect others than most.