Mistake? Are you saying they meant to give the boat a new coat of paint, and accidentally blew it up instead, killing a bystander in the process?
A mistake can be something that just turns out to be a bad idea. E.g. "we really need joins; using NoSQL was a mistake".
For a story that somewhat parallels what the French did (but a WHOLE different level) check out: http://en.wikipedia.org/wiki/Ramil_Safarov
If someone throws rocks at oncoming cars, you can't claim innocence because "I didn't mean to kill a family in a car crash!" If you invade an oil-rich Middle Eastern country and cause half a million excess deaths, it's just as bad as if you personally murdered each and every one of them.
On the actual statement - I disagree 100%, but we're talking ethics, so rational arguments can't go very far :)
If you read very carefully, you'll notice that person you're replying to was delineating between evil and culpable.
What you are doing is diluting the 'evil brand'. If you call a drunk driver evil, you have nothing left for the likes of Hitler and Pol Pot. What are they then - double evil?