Imagine this situation: Al Quaida calls the German police and tells them that it is about to launch a series of attacks at the Dusseldorf Airport.
The police ignore the threats.
Al Quaida then carries them out, killing hundreds. It announces that it did not want to cause German deaths and had, in fact, warned authorities.
Not only would Al Quaida come out -- in the warped minds of many European leftists --as the "good guys" but almost everyone involved, from the local police desk sergeant to the German PM would be avalanched in law suits. I would not at all be surprised if the German government fell as a result.