I think this is a very interesting thread. I have been very fortunate to have been taken to many fine dining establishments since I was about 2 years old. I was quiet, sat still, and never made a scene or fuss. To this day, I feel more comfortable in a fine dining room than in the local pub. I am always amazed to see ill-behaved children, and often more frequently, ill-behaved adults, in these restaurants.
In this situation, I think I would also be terribly annoyed. I would want to sm**k the little sh*t AND the parents.

In this day of rights and freedoms, I think we have forgotten responsibilities and duties that go with them. Most certainly, the parents should have excused their child and given him a stern lecture on appropriate behaviour. The Management could have asked the parents do the same and/or leave.
But in the bigger picture, this became a night which became undone. Unless this happens at this restaurant frequently, I think it is better to look at it as just one of those nights. A myriad of other occurences could have the same effect -- a fire in the kitchen, an off night for the servers/kitchen, power outage -- these are all things beyond your own control. We should also be grateful that we are in a position to be able to enjoy a nice meal out. Finally, we ought to be happy, and perhaps praise the parents, of those children one see's at restaurants who are very well behaved.