You'd be an idiot to try and argue a point without any evidence to back it up.
Watching television and movies may very well give you ideas about how to kill someone, but so do magazines, martial arts classes, various fighting sports, play fighting, and many other things that've been part of the world regardless of the existence of television and film.
And if you're now going to say we should take all those away too, then what the hell? Are you suggesting we just sit around doing nothing for fear that we might be shown a possible way of killing someone (which is a natural instinct of almost all animals upon this planet, I might add).
A killer is going to kill regardless of whether or not he sees new techniques for doing it on television. It doesn't take television to teach you that twisting someone's neck around 180° will kill them, as will driving a piece of metal through their torso. Killing is killing, and humans know their own bodies well enough to know what'd do the job.
Your whole "They might see ways of killing!" argument is crazy. In most cases television and film is based on real life anyway, so wouldn't it be just as influential to go look at all those police, soldiers, and mobsters out there carrying guns and killing each other at times?
I suggest you look into what actually drives people to kill, Fealiks. You'll find that in practically all cases it isn't watching a television programme or film that triggered it, but a loved one pissing them off or something like that. Perhaps you'll find a few fringe cases of it happening, but that's it.