Is it ok to call a foreigner out?

The other day, I was talking to this guy who kept referring to electricity as furniture. At first I thought I lost more hearing than I realized thanks to 20+ years of awesome stereo headphones, but no, he said it...like 3 times. I didn't want to say anything, because well, it was a professional situation and it was obvious English was not his native language, but other than that, his English was pretty good!

What is worse is that he had an American born friend with him who just kept letting him say "I need to transfer my furniture into my friend's name." I was so confused. I couldn't tell if it was a joke? Or if it was serious? Or if the friend was just too polite to call him out in front of a chick that he thought furniture kept his lights going.

Are you one of those people who tells someone when they have something in their teeth? Or when they have toilet paper on their heel while they prance across the Rooftop party or something?