Our Computers, Ourselves: Are computers changing human character?
npr.org
npr.org
IOW, human character is malleable and constantly changing. It's not surprising that something as significant as the Internet (not computers on their own) is changing us again.
I like to also compare the Old Testament from Deutoronomy onward and Gilgamesh. In Gilgamesh, which is a much older book, the world is vast, lonely and mysterious and man's primary struggle is with the forces of nature. In the Old Testament, the world is crowded and the the story line is dominated by near constant never-ending warfare.
Otherwise how do you explain what appears to be the majority of modern jihadists coming from at least the upper 1/2 of society, if not solidly middle class or above, e.g. the 9/11 hijackers?
Of course, your thesis doesn't have to explain all examples of being "rutheless".
As for your last point, hmmm. Is that in part a function of viewpoint, of e.g. the author(s) and audience(s)?
ADDED: other counterexamples: The Japanese in WWII, the actions of some high caste Indians towards lower caste ones. (As a matter of fact, in India in the last few decades, while incomes have gone up, calories and quality of them has gone down for those lower on the socioeconomic scale...).
That's to say the nice gal at the office who when she plays video games plays a sadistic character, that character is closer to her unfiltered self. So she is less the agreeable helpful persona --that's the role she puts on in society-- due to norms and expectations, and is more that violent persona. And that violent persona is not so much a reaction to balance her social mask, but more the "real" self. We can imagine why societies evolved to manage the true selves in ways that seem hypocritical.