I know that sometimes I'll tell Oscar to 'put that in your gob and shut up', but the tone could in no way be mistaken for anything other than playful. If he were upset (rather than just fidgety - I tell him to shut up when he's fidgety, not vocal!) I would just take him away from the situation that was obviously stressing his little system out and take it as a cue that he's overstimulated. Nothing is so important that I have to remain somewhere that is having a negative impact on him!
I remember serving a lady last year who had a VERY young baby (as in, less than 3 months old) in a pram who was hysterically screaming the store down. The mother was choosing earrings. When she came to the counter (I had been busy serving at the counter or I would have gone over to her sooner with my offer) I asked if she'd like me to hold her items until she could feed/soothe her child. Instead, she says "Nah, he can wait, plus it will make you serve me quicker with him screaming"...WTF?? I told her I wasn't going to 'go quicker' because I'd make a mistake and end up taking longer. Who put EARRINGS before a very young babie's cries for attention??? All she needed to do was come back! I still don't know how people believe babies are manipulative...