Maw I am still amazed that a film which terrified me and played on my mind (as a middle aged woman,) "The Woman in Black" the one with Daniel Radcliffe has a 12 certificate!!!
I'd have been damaged for life if I'd watched this supernatural horror at that age!
Your poor Grandson. I was absolutely horrified when I viewed on of the X Box games my (adult) son and his friends were playing. It involved players being killers and shooting or otherwise murdering baddies on screen. It was terribly violent, but players splattering the figures on in a gruesome fashion was greeted with howls of delight by the others,
They were adults but I know much younger children play these hideous and very violent games - some of them very tense and scary. I wouldn't allow my sons Nintendo boxes when they came out. They were teenagers then and I was viewed as a real spoilsport but I was so glad that their childhoods and teen years were spent mostly in the fresh air and not sitting in front of TV screens or video games/mobile phones.
I think parents have a duty to monitor what their children are watching. One of our young GDs tried to con us into letting her watch a Netflix programme designed for American teens. It was complete tripe but showed girls having dream lives, lusting after boys, using make-up, gyrating sexily to music, preening themselves, deceiving adults - all to pop songs with dubious (sexual) lyrics. We told her it wasn't suitable and distracted her, but she pleaded with us to let her watch it. We said no - and when I mentioned it to DD, her Mum, she too told me it was banned at home. Apparently a school friend, aged six, watches it and did while GD was at her house, supposedly playing.
My DD was very annoyed.
I do hope your chat with your DGS helped him but sadly, with children now having TVs in their rooms as a matter of course, one has to wonder when and where they'll be watching the next unsuitable film or programme.