Imagine the scope of human behavior on a bell curve. You have extremes of good and bad on either end with most people (and their subsequent actions) being somewhere near the middle (68% within +- 1 standard deviation and 95% being within 2.).
Now shift the mean in either direction. The normal distribution (bell curve) is still intact but the overall amount of good behavior or deviant behavior becomes more or less frequent depending on which way you shift it.
As societal norms shift so will behavior. As a society we have shifted the mean. We devalue human life and then are shocked when someone acts on it. I am explaining, not justifying. You reap what you sow. If we sow the whirlwind we reap destruction. That is where we are as a nation. As things which were once morally unacceptable become acceptable the mean shifts as does the whole bell curve and the prevalence/frequency of what were once considered extreme are now considered normal or natural.
When we shift norms like this the behaviors that were once in the extremes will become more mainstream (take marijuana for instance).
Few of us consider how our seemingly insignificant moral failings and indulgences contribute to the problem of a morally decadent and decaying society. We must do our part to shift the mean again and that means our beliefs and behaviors really do matter as they contribute to the culture we are immersed in.
Our nation needs repentance and it starts with us, Christians.