When I first saw this, I thought "wow, that's a pretty long entry as V entries go". Now I see why. I have been in that situation many times and it is an excruuuciating position to be in. I tend to either hold back as you did (though for different reasons: a.) I'm afraid I'll totally go off and/or b.) I'm afraid if I express distaste for the parent's conduct, the embarrassment/anger they experience will later be taken out on the child) or I just start cheerfully talking to the child, engaging the child, praising the child, etc. which most parents don't mind (and it damn sure gives the kid a pleasant respite). If the parent talks to me, I'm very warm, I smile, I charm them, I say what a beautiful child you have. =) =) =) I do that to make them feel good about themselves and their child, so they can take that good feeling with them. Even if they can see what I'm doing, it reminds them, it cues them, to behave similarly and to remember what's important.