Well, no more horror movies or gratuitous violence in movies or TV or video games, yes. It needs to be understood that what kind of entertainment there is affects people, but then, that's the point, isn't it? If a a movie or video game didn't affect people, no one would be entertained by it, right? People need to understand that if you put violent entertainment out there, that some people will be more prone to use violence to solve their problems, maybe even most people will find it more appealing, but only a few will go out on a shooting rampage against innocents. It is a cost/ benefit analysis, pure and simple.
At the very least, violent entertainment desensitizes people to violence and reduces compassion for other people. To what degree someone is affected depends upon the individual affected.
There is a social cost to violence in entertainment. That said, I like action movies i which violence is used as a necessary evil to defend against the bad guys or defeat them, so I am not personally interested in removing said entertainment unless I become aware of compelling evidence that the absence of same would make for a better society.
If I became convinced of the need to remove that stuff, then I would be irresponsible and arrogant to oppose it's production as much as I might personally like it.
If it could be proved that "No more violence in movies, no more action movies, no more video games, no more songs with suggestive lyrics." would save one innocent life, prevent on psycho from flipping their lids and killing people, WOULD that be enough of an incentive to indeed prevent the production of that entertainment to you? It is a relevant question. How many lives would need to be spared, or how many killers would need to be prevented? What is an acceptable cost/benefit ratio for YOU?