I guess opinion is more subjective and relative because when I've gone to the theater to see PG and PG-13 movies such as Guardians of the Galaxy, X-Men First Class, The Hunger Games, Man of Steel, Maleficent, Snow White & the Hunts and NOAH I saw quite a vast array of children which appeared to be as young as the ages of nine or eleven with their parents. I know personally know families who have taken their kids with them to PG-13 movies and who continue to do so often. Again, I believe that it's all up to the parental discretion of the parent. When I saw Man of Steel, X-Men and NOAH at the theaters it was more sons and their dads at the movies. My personal opinion for a movie like True Grit or The Fast and the Furious I wouldn't take a child under the age of 11 or 12 to see either of those types of movie but I would take a 11 year old to see a movie like Kingsman The Secret Service.
But seriously, I agree that Batman Death of the Family isn't the best comic story arc to share with a adolescent under the age of at least twelve but then again it depends on what that kid is able to handle mentally. I've seen kids reading some manga which can get pretty dark. Even Naruto get's dark and lots of kids around the age of ten read that. But really, Marvel Comics and DC Comics is in my opinion are safe for kids ages twelve and up. Stuff like Superman and Batman is what I was raised on by my parents as a kid and I'll raise my kids on it. I grew up watching the Tim Burton Batman movies and watching the dark cartoon Batman The Animated Series along with Justice League Animated. DC Comics and Marvel have an appeal that transcends age and that is as it should be. Heck, in my day kids grew up on stuff like Jurassic Park and re-runs of the gritty Indiana Jones movies. What the heck? Are we going to go soft now all of a sudden?