I don't know, a week of lost sleep seems like a pretty cheap price to pay for not growing up into the average "TV shows gory pictures of terrorists blowing up something? I now have PTSD and will vote for any measure that you say will make it less likely that my sensitive eyes are exposed to such revolting material again" member of the American electorate.
I was left to roam the internet freely starting around age 10, saw my fair share of liveleak-style material, lost some sleep over it and grew up into what I like to believe to be a fairly well-adjusted adult who can only shake his head at the sort of things people in his generation experience irrationality-inducing terror over.
From my observations, the effect of disturbing content seems to depend on the person. Some people see it, are disgusted by it and are largely unaffected. Some people (like myself), see it are disgusted by it and then are bothered by it for a long time.
I've noticed that my son is the same way, so I tend to be very careful about what he sees. He's definitely more sheltered that some of his peers, but that's based on how he reacts. It's important to know your kids and know how much they can handle.
Even if there was an initial difference, it seems unlikely that sheltering him would do anything other than exacerbate his comparative inability to deal with such material. While this is obviously just anecdote and open to interpretation, I have noticed that instances of various form of mental trauma due to inevitable predicaments of day-to-day life (e.g. non-lethal car crashes) are very common among my American acquaintances, but practically unheard of among the European ones (who, for a variety of reasons, tend to be brought up in a much more hands-off manner as far as media consumption is concerned).
If a child is afraid of swimming, most teachers would find it reasonable to keep pushing and gradually acclimatise them to the notion rather than give up and say they are just not cut out for it; why would whatever reasoning that underlies this not apply in the case of "disturbing content"?
I was left to roam the internet freely starting around age 10, saw my fair share of liveleak-style material, lost some sleep over it and grew up into what I like to believe to be a fairly well-adjusted adult who can only shake his head at the sort of things people in his generation experience irrationality-inducing terror over.