Tuesday night's All in With Chris Hayes segment set out to analyze Starbucks' new Race Together initiative. But one exchange ended up being as hard to listen to as the ones critics predict could happen when baristas chat about race relations.

In response to vlogger Jay Smooth's popular 2008 "How to Tell Someone They Sound Racist" video, Hayes' other guest, Nancy Giles of CBS Sunday Morning, made fun of Smooth for the way he spoke — seemingly because his light complexion made her think he was a non-black man attempting to imitate African Americans.

"I can't not tease Jay about the kinda, like, brotha way he was trying to talk, like, 'Hey,' with the rap music in the background, and, like, down with the people," Giles said around the 5:20 mark, adding (after Smooth interjected, "I'm a rap guy!"), "There would be some people that feel that you co-opted something like that, and other people might feel like that's his background and that's really cool, too."

Eek.

"It's also interesting because I'm actually black, but you assumed otherwise," said Smooth. Tying the confusion back to the topic at hand, he added, "and this is the sort of awkwardness that we can look forward to at Starbucks across America."

(Side note: watch Hayes' facial expression as this all happens. It's possibly the most underappreciated part of the exchange.)

Giles later said she knew Smooth was black. But she had a hard time convincing viewers who watched the segment that this was the case:

@mwpolitico @jsmooth995 but FYI I knew Jay was African-American. Was intrigued by the voice on the video vs the voice of the guy next to me — Nancy Giles (@nancygilesnyc) March 18, 2015

If it was in fact a mistake, it wasn't so much a reflection of a particular shortcoming on Giles' part as it was a reminder of how complicated this whole race thing is, and how many different factors besides skin color inform identity. Lesson: you really can't look at people and decide what their background is or what they call themselves, ever — especially not on national television.

Further reading

Starbucks' push to make baristas talk about race sounds like it could be disastrous

These twins can teach us a lot about racial identity

11 ways race isn't real

WATCH: 'Race isn't biologically real'