File this under you've got to be kidding!
Now whistling Dixie is offensive? Well, Y'all are just going to have to be offended. (Yes, most people I know stand when they play Dixie.)
I figure if Kevin Spacey can sing the entire song on House of a Cards its not a federal crime, at least not yet.
Finally the staff member was whistling the song, that is without out the lyrics (which aren't really offensive in fact) so how could anyone except maybe Brigida Mack be offended?