Seeing someone partake in racial humor? This might help them understand why that's not okay.

So true! You don't start by saying "X group is less than human, let's kill them", you start by saying "Let's laugh and agree that X group is less than us."

And when they laugh, they agree.

*Takes ultra deep breath*
Spot on. The term is "Overton window." At first banning a free press is too extreme. But first you deregulate content guides so organisations can say what they want under the guise of increased choice. Then you say that the ethical media doesn't always cover the "facts" (that you make up). Then you keep lying so that when they call you out your supporters call them "fake news". You then start hitting them with tax evasion and other things so that they secretly give you control. After a while enough people don't trust them allowing you to regulate their content under the guise of truth. At this point you have gone from ethical media that shares the facts to puppets that do what you want. Reagan did the first. Trump did the second, third, attempted to do the fourth when the DOJ "investigated" NYT, and attempted to do the fifth when he wanted to repeal section 230. We were lucky this time but will we be as lucky the next time?

Pretending that a word like "mayo" is a slur is also a microaggression/casual racism. It's a strategy to downplay the experiences of those of us who have experienced the real thing.