Indeed. I saw Sin City (an exceedingly violent movie) in a theater. A woman (presumably the mother) and two young boys (~8 and 11) were seated in the row in front of me. She didn't bat an eye at the violence, but yelped and shielded the boys' eyes when breasts appeared. I still don't really know what to make of that.

Wow. That movie is so violent I wish I hadn't seen it. I won't watch Sin City 2. I can't imagine how I would have felt watching it at that age.

I've not seen it at all but you're right that there are some strange attitudes with some people and letting their children watch horrific things at a young age. Even on this very topic, some of the comments are "meh violence isn't a problem, I don't see why it would be disturbing to my child" which is clearly a case of desensitisation influencing the stuff they show to their children.

I have same many films that I wish I had never seen as I can't "unremember" things or wipe bits of my brain out. The incessant flow of violence in films only serves to desensitise: something is truly shocking the first time, not so the next time, and repeatedly it isn't shocking anymore.

To see that some people use their own level of how shocking a film is to THEM to decide whether to show it to their children is distressing; "I wasn't shocked, so why would my children be??". Very sad.