I can disagree with that statement on some pretty simple grounds: a culture will dictate how certain bad seeds will act.
Evidence: Our culture doesn't have its bad seeds strapping explosives to their chests screaming Ballyhoo Snackbar in a marketplace and blowing themselves up. The culture of the 50s was more about bad seeds roughing people up a bit and moving on.
There is a cultural component to this, believe me, and it is steeped in what liberals are doing to society - diminishing the value of life, removing God, refusing to talk about the eternal consequences of your actions, and preaching moral relativism over the existence of absolute good and evil.
Culture determines what is an "unthinkable act".
In the past 50 years our culture has morphed to the extent that acts of violence and contempt for human life which would have been considered intolerable in media except as studies of horror are commonly piped into the living rooms and culture of America hourly. There is a lot of material which would have been considered 'X' rated (or worse) and definitely not the fare we raise children on. Even video games have kids routinely performing electronic slaughter (no, I'm not demonizing video games, as long as people are aware that that is just a game).
We played 'Army', too, without such aids, with dirt clod grenades and everything from sticks to toy guns, but maybe that more rough and tumble version emphasized that real humans can get hurt, and that pain isn't pretty--especially wen it is yours. Such things teach compassion as well as provide a venue for sorting out leadership (like pack order in wolves).
But 50 years' ago the list of unthinkable acts was considerably longer, and there were more gradations of solutions to problems between people. Confrontations had a spectrum pf possible outcomes, but few things were seen as cause for taking another life, not like today when somehow 'dissing' the wrong person can get you shot and killed. That all or nothing polarity, live or die, with us or against us mentality has crept in to the point where simple and civil disagreement is off the table for many, even older people because of the mindset developed in pop culture and entertainment which spills over into real life.
Those of us who watched John Wayne had the thought that "He can't learn nothin' if ya kill him.', instead of the Boyz in the Hood mentality of thet MF'er has to die. But one of the first cultural taboos to fall around the time prayer was eliminated from schools (with the idea that there is an ultimate authority we all will answer to in the end) was the sanctity of human life. With Roe v Wade, the door was opened to the greatest slaughter mankind has known, perpetrated not upon a vicious enemy, but upon our own flesh and blood, the most innocent of whom were the target.
What good can come of a culture thus corrupted? The only surprise is that much good prevails and these incidents aren't far more commonplace. .