Do not Buy the Quick Cheap Premise to Explain Evil.
The same way that watching porn will not transform you into a rapist or watching Top Chef will not make you open a restaurant, watching videos of killings will not make regular people become the next super murderer. We have shown many graphic videos because I have always felt 99% of people do not understand how quick and how violent true criminals can be. The concept of violence by most people is the tailored and choregraphed pablum we see on TV where the 125-pound rookie female cop tackles a 250-pound Roid Raging male single-handedly and in 10 seconds flat.
Paraphrasing John Ross: It is not the reason but the excuse. We have grown accustomed to desiring the quick/easy/understandable answer expressed with authority because we seek going back to our normal lives ASAP and we need to be reassured we can. But by now we should know better and prepare accordingly or we will fail miserably and possibly deadly when the time comes.