If they know what it means, then it's no big shock to their systems, and if they don't know, then it's meaningless to them.
So9
I'm sure they never hear those words in school in Detroit.......
Dont' be worried that they will know what it means. Be worried if they DIDN'T know what it means. If they see it explain to them that it is not nice, should not be there and then move on. For heaven's sakes you'd think kids were made of porcelain. Should the guy have done that? NO. Absolutely not. However, if my kids saww it I wwould tell them that is NOT how you make your feelings known. I wouldn't think it was gonna damage their pschye for heaven's sakes. Don't make a big deal out of it.