It's not an excuse to do nothing except with lazy people who will use ANY excuse to do nothing. It's an explanation of WHY that person is so effed up. They're evil. Still gotta stop them, but some people are just evil.

Now pretty much all "evil people" had INCREDIBLY abusive childhoods, with few exceptions. Even that 11 year old multiple murderer in England. Evil - how could someone that young do those things to 4- and 6-year olds, have a body count, unless she's just evil? Then you learn about what her "mother" did to her. That's a better Why than "evil," because it's a Why we can try to short-circuit. But either way, "because Evil" is not an excuse to do nothing.