Do Parents Allow Their Children To Be Exposed To "Mature" Content?

If I had a dollar from each parent who ever said, "My child is mature for his/her age," I would probably be a millionaire. Most parents tend to give their children a lot of credit when it comes to good looks, talent, intelligence, and general kindness. But is it wise to have children mature fast? Is it a good thing to have a mature child? Is it okay for young children to watch "South Park" (rated M for mature) and play "Grand Theft Auto" (rated M for mature) before the age of 17? What do you think? If you are a parent or grandparent, do you think it is okay? Do you think kids grow up too fast these days? Do you think exposure to violence at an early age makes children "de-sensitized"? Please comment below.