There probably isn't a singular root cause to this. It could be the constant imagery of death and crime on TV, video games, etc that creates a numbing effect. I'm sure the lack of a support system at home and in the family is part of it. It could also be a general lack of community, where people would rather keep to themselves than get to know each other. How many of us text and send emails more than we call and speak to people? My hand is raised. I'm as guilty as anyone.
As for the brats of today, it's rampant. I feel like my generation is failing when it comes to raising kids to be respectful and decent. I see it all the time with my boys friends. The friends think nothing of not only talking back to their own parents, but to me and my wife too. We have to tell the 9 yr old next door that they way he speaks to us will not be tolerated in our home. And if he doesn't like it, he is free to leave and not come over. And the general, "gotta have it now" and sense of entitlement. Geez, some parents make it tough for the rest of us to be parents.