Your argument hinges on the assumption that porn and gore etc. have worse impact on kids. I don’t think there’s a concensus on that. One might argue that porn and gore could have been found in print before the internet, but that social media have a more novel impact.

I personally like the theory that most kids problems are actually attributable to family issues. That kids in solid family environment/upbringing will not be “destroyed” by computer games, porn, gore (2 girls 1 cup anyone?), or social media. But that’s also just a theory.