[CrypticCuriosity]

I think you answered the question when you said it "opens up their minds" to scarier possibilities, and how they handle that. I believe it's usually a case by case issue for older children, but for the most part no, I don't see any reason to expose young children to horrible violence/gore/scares/etc, because you may think they can handle it, but you don't know that for sure, even as a parent. They do not have the coping and reasoning mechanisms in place to process what they are seeing. And I know some people will surely come in here claiming they watched all matter of horrible content as children, but they should realize they are most likely the exception.

For older children, it's knowing their temperament and what they can handle, and never, ever pushing them (as some parents tend to do). My older sister took me to a haunted attraction when I was around 10 or 11 that I thought I could handle it. Halfway through, I was apprehensive to continue, which my sister noted and had us leave the attraction then and there. It was a good exercise in me getting to know my own limits, and I'm thankful I wasn't made to finish the haunt. I take the same approach with children in my family. If they tell me they can handle it, I'll let them try, but I'm watchful of their reactions. Younger children, it is your job as an adult to make the decision for them until they've had time to figure themselves out a little better.