While I waited for the previous customer to finish, and while I paid, I listened to the vendor having a conversation with a friend. They were going on about how rude all of the Mexican vendors were in the market and how they didn't seem to want your business. The conversation shifted to the vendor's employees, wherein she started ranting about how one of her employees refused to do something (though she didn't say what) and how all Mexicans were lazy and they stole stuff.
I was aghast. Unfortunately, I already had stuff picked out and was about to pay, or I would have walked away. Instead, I finished the transaction and spoke up. "Pardon me, but that conversation really isn't attractive to your customers. I'd really rather not stand here and listen to you talk about people that way." (Note that quite a few of the vendors, including those near her stall, are Mexican.)
"But I'm talking about my employees."
"OK, then talk about your employees. Don't talk about an entire ethnic group because of a few people-- that's just bigotry."
"My employees live on my farm for free. I pay them. And they still steal three thousand dollars a week from me."
"Those are your employees. They're not all Mexicans."
I regret having bought anything from her, and I'll avoid doing so in the future.