You want evidence that rises to the level of establishing "causality" in consideration of a natural experiment that is being run across all of humanity simultaneously?

What populations are protected from violent media?

How would you even disentangle all the countless confounding factors?

The arguments here are well-worn by the industries that peddle in these types of media, with obvious incentives, and obvious incentives on our side as consumers to not be restricted from consuming whatever we enjoy.

This is why I spent so much time referencing all the other ways in which humanity tends to emulate the behavior of other humans or be influenced by advertising/media, as it seems unlikely that these tendencies would suddenly cease around the sole category of "violent media".