Do not say racist things at my work because I will call you out on it.
Case in point: An older white man comes up to the counter and directs me to not let the black boy, who'd just walked out, back into the store. I was caught off guard and asked why.
"Believe me, just don't let him back in."
"Uhh...yeah that's racist."
"Whaaaat. What do you mean?"
"You're a white person instructing another white person not to let a black child back into the store on a hunch you won't reveal."
"That ain't racist. Oh, I'm a racist now?!"
"Please bring anymore racist remarks up with management. I have a job to do."
He started running down the aisle screaming to anyone that would listen that I called him a racist. He grabbed his wife, left a cart full of groceries and stormed out.
The best response though was management. After I explained myself they told me to watch what I say to customers. Yeah, of course, wouldn't want to make the customer angry, right? Fuck that.