If anything it's people with problems that tend to search for such things rather than such videos causing something.

Somehow they failed to be horribly scarred by it.

https://medium.com/the-ferenstein-wire/the-birth-and-death-o...

Over the centuries it's been sanitized and Disneyfied, but the primal drives that fascinated by that sort of thing have not gone away.

Also half todays cartoons would not pass neither comic code nor restrictions at early movies.

In the US, there was no comic code or movie censorship, but there was things like Comstock laws. Would Walt Whitman's "Leaves of Grass" raise many eyebrows today? It did in the 1850s-60s. (http://www.unm.edu/~unmvclib/handouts/bannedboston.pdf)

It is true that Grimm's tales were at first meant to be more of an educational archive of folklore that otherwise would have been lost. (https://www.neh.gov/humanities/2015/marchapril/feature/how-t...) However, apparently, it was found after publishing that the stories appealed to parents and children. So between the first and seventh edition, apparently the stories were made "more appropriate" for children of that era. (https://books.google.com/books?id=6gX-hNshMJEC&lpg=PR39&dq=M...) In those times, that more meant getting rid of any bawdy humor and any references to sex (violence to a "morally correct" end was okay though).

Culture changes; it seems like nowadays, some degree of bawdy humor is okay in children's entertainment. However, I've seen many articles wondering if the Grimm tales are too scary for kids.

The comic code and movies are simply two additional examples of historical censorship.

It is pretty much impossible to defend comic code as written, even ignoring the argument that adults should be able to read horror stories (including those grittier then Game of Thrones) if they like them. Comic code was simply a reaction of people unable to suddenly process that many have different preferences then them.

Try watching disturbing violence (war images/videos for example) for a while yourself. Empathic response will blunt itself within a week or two.

But I'm weird and think that it's far better to let children see sex than even regular hollywood violence, and that things like US military recruitment ads and ISIS recruitment videos should be treated identically (restricted behind a warning that they're not for kids). The normalization of violence is a terrible thing.

Trouble with children is that they may not yet have the moral compass for lack of a better phrase. I would find it important to talk to the child and ask him what he's thinking about the videos, and make sure he understands that the behavior in the videos is horrible, ends the life of another person, what that means, etc. I'd also make sure the child would not get trapped in some cycle of feeling guilty for simply watching some videos and having/not having whatever reactions to it.