"Trouble is your thinking that merely because white Americans voted for a black man they can't be racist."

I've suggested nothing even remotely similar to that.  In fact, using the Socratic method, I take that assertion at face value and assume it to be true.  Then, assuming it's true, I plug that belief into a logical argument.  This is known as reductio ad absurdum.

So let's assume there are 60+ million racists in America because William says that anybody who votes for Trump is automatically a racist.  Simultaneously, if these people voted for Obama in a previous election, that does not mean they aren't racist.  Somehow, in this world, no evidence of racism does not indicate a lack of racism.  But, again, voting for Trump is considered automatic proof that a person is racist.

This is preschool level logic.  How could anyone with a college education think that argument makes any sense at all?  Are you even capable of thinking rationally about politics?