There's only one way to settle this.
What I want you to do is print out the Racial Thermometer (tm) and question a cross section of the population to see whether [the person on the radio] is a racist.
When we have good cross-section of black opinion from around the world, we'll collate the results and have our definitive answer.
Until then, I'm going to keep an open mind on the matter.
Remember, you're only questioning people whose skin colour matches the right hand side of the card.
For best results hold the card to the cheek or forehead of the questionee.