I find it extremely insulting!
It happened to me; a guy did it! I spun around and said loudly; "If you want to keep your teeth, I suggest you keep your hands to yourself; unless of course you'd like to ask me out on a date- if so, help yourself sweetheart".

His friends roared with laughter, and kept calling him 'sweetheart' . He was most uncomfortable. (Didn't ask me out, by the way).