Take, for example, the recent riots that occurred at Woodstock '99. The problem with confusing explanation with excuse is that it let's the perpetrator off the hook. In effect, we are asked to accept that the person didn't do it, the explanation did. This line of thinking is endemic in much of modern psychology. While studying to become a psychologist, I came under the influence of several professors with a behaviorist bent.
Freudian psychology says much of the same thing, but with different language.
Unfortunately, this kind of thinking is not confined to psychology. With the introduction of the social gospel at the end of the 19th century, individuals were no longer seen as responsible for such behaviors as drinking, drug use, debauchery, or criminal behavior. The same is true for the current enthusiasm for early brain development. I'm not suggesting that these factors don't matter when it comes to human behavior. Of course they do.