You also seem very flip with how you characterize people of color by using the "darker than copier paper" description. Obviously, you are not familiar with the "brown paper bag test" used to discriminate against darker skinned blacks in this country. If you did know, then shame on you.
The argument about stifling speech is irrelevant. We do not need outrageously offensive acts to occur to justify diversity or any other training. You do it because you believe in its ability to improve you business organization. Because it is a value. Not as a stop gap or a cork for loud mouthed pitchers (or anyone else).