You know, S., I do think that there are plenty of scary moments, at least from a child's perspective, which don't make the news because they are domestic situations or ones in which things can feel scary or out of control, but no one calls the police.
My son and I watched "The Red Balloon" together when he was four-- he found it boring. I found it refreshing in some ways that there weren't adults guiding the children's every move. That said, I do know the world is different than it was when I was a kid.
Take cell phones for example. Cell phones cause distracted drivers and cause a lot of accidents and deaths. This was something I didn't have to worry about when I was a kid-- does the driver see me crossing the street? As an adult, the reason I limit my son's independence is because there is high traffic in our area of town; our street is used as a cut-around for people who are in a hurry-- and they drive like it. When I walk him to school, on average I see at least two or three distracted drivers at the main intersection. So, while it would be great to let him walk to the corner store by himself, I KNOW he isn't ready yet for that responsibility-- I haven't seen him display that level of awareness that will give me reassurance that even if the driver fails, my son will catch the mistake before it becomes an accident..
I let my son watch tv shows which don't feature a lot of relational aggression because I don't want to see him behaving in the same ways those characters do. I am actually more comfortable with him watching some minor violence (not that he asks for it or seeks it out) than I am with him watching characters being mean and nasty to each other. Mainly, because this is what our family values. He doesn't need to learn how people are unkind to each other... I'd rather him see how connected we are as a people and a planet, so we find media which reflects this.
As someone who was molested during the 'good old days' by a family friend, I can say that I am thoughtful about the situations I leave my son in. Some people might call that over-protective, but I think it's more about not making him be more mature than he is. I think my son is worldly in to some degree- he knows about the physical world around him; we have seen a lot of different things on our adventures around town, some things I honestly wish he hadn't had to see. (We have a large homeless population here, a disproportionate amount of whom are mentally ill or deeply struggling.) I try to explain with compassion as well as helping my son be aware of what the boundaries need to be-- that some people really need their space and just aren't doing well, so we need to be careful *for* them.
In regard to the movie," Sean", I think I can say that knowing about drug use at four speaks more about his parents having sh*t boundaries than anything else. That's not to be admired in any capacity. My child knows about alcohol and intoxication, but through constructive conversation, not because we were modeling drunkenness.
So, I don't think I am deliberately shielding my son from the world, I just try to be thoughtful about choosing experiences and media which teach him about what's important to OUR family. Those choices won't be the same as any other family, but I am not worried about what everyone else is doing with their own kids... I will leave that to them. For me, worldly isn't about what sort of movie to watch or not to, but it's about having the ability to move about comfortably in the world and get along with people, and my son is not yet seven, but he does have this.