1. I dunno, Sypher. I suppose some would make a case for Accuracy in Reporting (the same ones who would scream "Artistic License" for altering the facts for drama!)The special FX are there to do it all with. I suppose the bottom line is what sells; the public dictates what it wants to watch by the box-office sales. By those numbers, we tell the producers what we want to see. As for me personally? No, I don't think it's necessary. I spent a law-enforcement career investigating homicide, suicide, accidental death, death-by-auto, unattended death, ad nauseum; if death was involved, it hit my desk. No, I don't need to watch Hollywood depictions of a script-writers idea of violence. My movie-going dollars won't show up in those numbers.
2. Violence by movie compulsion a defense? Absolutely, positively, irrevocably NO! The M'Naughton Rule aside ("irresistible impulse" - more Supreme Court follies), none of these poor, misguided waifs are "compelled" to do anything. They WANTED to do it; they thought it was "cool". They may have gotten their specific ideas from movies (or music), but it "compelled" them? Phooey! As Nero Wolfe would say, "This is flummery, of the highest order!" Indeed it is. The snakes (aka attorneys) for the defense have discovered a new gimmick to foist off on weeping, bleeding-heart jurors who are soaking it all up.
Guess I'll stop now, Sypher. You asked for an opinion, not a philibuster. Good Questions!