@oristarA,
I have extensive experience in this matter.
Immunity to the notions of physical death of others, can in no way arrive entirely as a result of playing computer games unless a break from reality occurs in the subject.
Watching movies and identifying with the hero, counters this entirely... Immunity to the death of other physical presences arrives through two major avenues..
The first and most obvious is birth.. We are unaware unless taught, that other lives are incredibly relevant, or indeed that death of them is possible.
The second way is through desensitising, yes, though it is not as basic as that, nor is it as easy as often implied. Generally, massive factors of pain and/or hatred, often combined with attacks upon the subject are required to create it.
That this concept is applied in others minds to attitudal expressions of 'what needs fixing' as a break in reality, is not the flaw of those you witness, describing the point.
Application of the same values cannot apply in 'isolated' occurance outside the grasp of science, unless the entirety can be mapped and monitored.