Brian McKnight performed the National Anthem with two of his sons before a NASCAR event yesterday.

But one of the boys was wearing a hat, and just before they started, someone yelled at him to, quote, "Get that [crap] off your head!"

Here's the full story with video

WARNING: It's UNCENSORED.

By the way...one of Brian's sons calls himself "Broken Robot BJ". What's THAT about??? I feel embarrassed for the NASCAR announcer who had to say it over the loudspeaker.