I guess I make a distinction between what I would call "traditional" (for lack of a better word) homicidal violence---gang murders, drug murders, you-dissed-me rage murders, etc.---and people, especially, kids killing because, e.g., their parents impose a curfew.
People may not consciously think life is cheap, but I believe growing up in a culture infused with the idea that if someone, even someone YOU had a part in creating, is inconvenient for you, it's okay to kill that person and throw him in the trash, has consequences. For everyone.
Abortion is probably the most telling example, but the issue seems to me to be even broader. It's the ME-culture, the widespread conviction that nothing and nobody should be allowed to stand in the way of an individual's personal happiness. Obviously, David Ludwig believed that. It seems that Matthew Niedere (the boy from Minnesota who murdered his parents) agreed, as did the friends who helped him. And why wouldn't they? Even the churches today preach a doctrine of Self-Fulfillment.
People have always been most dangerous when their heart is threatened, and that's what they thought was happening here.