I'm not going to get into all the various obvious reasons

African-Americans overwhelmingly vote for Democrats, other than the fact they have no reason to vote for the Party taken over by southern whites who were Dixiecrats; whose candidates call their property things like "Niggerhead"; like to put on tricorner hats and impersonate the founding slaveholder de jour; who are quick to get the needle ready if the inmates non-white; and love to call any black politician un-American and/or socialist. But I'm going to guess calling African-Americans "brainwashed" isn't going to change the dynamic.