I recently found out that a visitor to my home considers me a racist ...

[bravenak]

191. No it's bigotry. The system did not back him up.

The words mean similar things but not the exact same thing. The dictionary definition just wont do.
Just like when creationist use the word theory like a layman. In their world a theory is just a guess.
When we use the term racism, we are not using the sixth grade definition. We are using the sociological definition of racism.

Institutional racism is a pattern of social institutions — such as governmental organizations, schools, banks, and courts of law — giving negative treatment to a group of people based on their race. Institutional racism leads to inequality; sociologists use the concept to explain why some people face unequal treatment or occupy unequal statuses. One historic example of institutional racism is the barring of African-American students from attending certain public schools, which limited the students' educational opportunities and helped prevent them from achieving a status equal to that of others. Institutional racism need not involve intentional racial discrimination. For example, individual judges might intend to impose similar sentences for similar crimes; yet if Caucasian people tend to receive lighter punishments, plausibly institutional racism occurs.

Thats why we also do not tend to call women sexist even if they hate all men just for being men. Because historically our group has no power to back that up or an institutional system that keeps women on top. The ism in this situation to me comes from the power. In america the black race has been oppressed so much that a black man walking around hating whitey with all his heart, is merely an oppressed bigot, not a racist. He has no power the keep white people down as a whole.