I fail to see the big deal as parents should be the ones making this decisions and not legislators or retailers. I have no problem with a law that restricts the sales of rated material to children as long as parents are allowed to make the final decisions. Now if the law says parents cannot purchase the game for their child, then I do have a problem with the law. Different kids have different reaction to different stimuli, parents and not the government should be the ones to make the decision for what is best for their child.
Face it children do not have the same rights as adults including the right to free speech, parents still have some control while children attempt to learn how become responsible enough to be able to cope with those freedoms.
One more thing, look at Joe the camel or the Marlboro Man to see where government has the right to stifle free speech.