From a forum post about an unruly child who was slapped in Wal-Mart by an unrelated adult, by "Worldwalker." I really love the last paragraph.
"Speaking of kids crying really loud, no, you do not have a right to allow your kid to scream in a store, a restaurant, a movie theater, or anywhere else where civilized behavior is expected. You have no more right to do so than I have to play the bagpipes there. Of course a 2-year-old isn't mature enough to be responsible for his own behavior ... which is why it's your job to see that he doesn't do uncivilized things. That goes with this whole "parent" thing. Having a child is a major responsibility, and part of that is accepting that taking proper care of that child is going to require some changes in your lifestyle. You can't go on as if nothing has changed and demand that other people endure the consequences."
"If you've got a child who's too young to behave in public places, then don't take him into those places until he's old enough. Leave him with Grandma for the afternoon. Get a babysitter. Shop online. Get the movie from Netflix, with the added bonus that you can watch it without being distracted by the heavy breathing three rows back. Get take-out."
"Your right to swing your fist in the air stops where my nose starts. Your right to let you child do whatever it wants stops where other people's rights -- what's called "quiet enjoyment" start. It's like we're starting into a social tragedy of the commons, where people take a little bit more, and a little bit more, until eventually have a world with all the charm, pleasantness, and civility of a cage full of poo-flinging monkeys."