It's possible the little boy was the one with the hospital appointment so needed to be there.

I have never believed in making threats I can't carry out. Does no good for the child who will soon learn that the threat is baseless. Making authority figures into bogeymen is a no no as well. At the very least one of the parents could have picked up the child and taken him outside for a few minutes to calm down. I would agree with Scoville - spend time keeping the child occupied. Most waiting rooms these days have books and toys for kids and it isn't difficult to actually bring some of the child's own toys or books along to keep him busy. Problem is, some parents don't play with their children - they let the TV do the babysitting.

Just an aside - why give a 2-3 year old a computer? Surely at that age their are better educational toys to work with!