Personally If I had children I can say I would not take young kids to violent horror movies …and I don’t think most would… I go to the movies every week and I almost never see kids in R rated movies even Deadpool I did not see any… which I was surprised at considering the character is now apart of the MCU…. I may take a teenager depending on the situationI believe exposing children to age-inappropriate content can be harmful to their development and mental health. So from that perspective, I certainly do care if parents take their children to see violent horror movies. That the US (together with Anglophone Canada) is such an exception in this regard should tell you something.
ETA: To be clear, I don’t count Deadpool and Wolverine among those films that would cause a child harm, even if I think it’s inappropriate viewing for them.
With that said I don’t think I am in the position to tell others how to raise their kids… as someone who grew up in the 80’s at the height of the slasher flick… I knew plenty who watched such content and they turned out alright