The defense of the campaign tied up valuable resources that otherwise would have been deployed offensively, it's as simple as that.Defending against a sustained bombing camapign was very costly for the Germans, let there be no mistake or misinformation in that regard. Where most of the criticism of the Bombing campaign arose is becuse claims were made about what it could do before and during the war, that it simply could not do. Countries could not be brought to surrender by bombing alone. From those bombastic and embarasing claims has arisen in the postwar endless debates, the opportunity for revisionists and German apologists to raise questions about the fundamental failures of bombing on a much more generic and widespread scale. none of these postwar aopologists and revisionists have much to go on, but it hasnt stopped virutally an entire cottage industry springing up to support the various notions that are carried with it.