I was shopping for a few things at the grocery store, making my way down the greeting card aisle. At that moment, the song "Eternal Flame" by The Bangles came on over the loudspeaker and I started to sing along. Not super loudly or obnoxiously, mind you--and I've shopped in this store many times and sung along to the music without any problem. But I turned the corner at the end of this aisle and was passing by the one next to it, in which there were two store employees (I believe one was stacking something on the shelves) talking to each other.
As I passed by, I heard Shelf-Stacking Guy say "I'm so glad we have the new version of this song with the extra singer!" in a very sarcastic/rude voice. I didn't even realize he was delivering an insult at first, but after I passed the aisle, Shelf-Stacking Guy came walking out from it behind me and started mock-singing the song, as if to make fun of me.
I'm not saying anyone has to like my singing, including him...but to make fun of me when I'm barely three feet away? Not cool, and definitely not professional. It didn't hurt my feelings so much as make me angry, and I keep wondering whether to go to customer service and say something, because I have been shopping there a long time. Ugh.