When do kids become fair game for criticism?

Ok I decided to revisit the tea party of San Francisco on 10/16/2009. So yeah that kid was there and he was holding that sign, and right behind him was his mother. I wondered if it was his mother who told him to write that sign. I also wondered who ever told him that Obama was supposed to be the Messiah. There were these actors i guess making fun of the people of the tea party by dressing up as the rich people who these teabaggers make filthy rich. One of these people saw this kid and decided to walk up to him and start saying stuff to him. I could not hear exactly what she was saying but it was enough to make the mother say "he is only fifteen". Now is that a valid excuse for him not to be criticism by the actor woman. If he is only fifteen then why is he there in the first place. How do you allow a kid who is only fifteen to criticism someone else but he cannot be criticized himself. To me that makes no sense what so ever. But he was not the only one, there was another kid holding a sign. When someone said something to her, her mother started yapping off about respecting the fact that she is only a child. How can you bring children to an event like this where you are stating you public opinion about some one in such a uncivilized manner at times, yet you feel as though the children that you brought are not fair game. So what do people think, when do children become fair game for criticism? And do their parents have the right to try snap at the people who criticize their children when they are in the wrong?