My 9 year old said something that made me cringe!!!!

We were in Walmart, and a little girl was looking at him smiling and waving hi. I asked if he knew her from school, or sports...he said he didn’t. So JOKINGLY I said “awww shucks maybe she like you bro!! Go get her number” TOTALLY KIDDING!! His response was:

“Ew she’s too black. I don’t like dark black skin girls.” 😤

We are African Americans, well I’m not fully 🤷🏽‍♀️ my dad is Cuban and my mom is black and Dominican. But my sons father is AA. We have light skin. Only reason I’m saying all that is, I love AA people. I love all people, but when he said that it made me cringe, and I felt horrible. I am never partial towards one specific race. But I just didn’t know what to say to him so I said “that’s not cool to say babe” but he wanted to know WHY. “Why isn’t that cool to say mom?” Then he thought I was mad and it got awkward. What type of conversation should I have with him. What should I say? What would you do!?

EDIT: I just want to thank those who aren’t being judgmental.