...
Speer had it right, the need to produce AA guns and fighters to stop the bombing meant fewer resources to other fronts which had long-range benefits.
....
The thing to watch out for is application of Speers remark to the entire war.
...
Imagine a German Army approaching Moscow with a third more artillery, thousands more aircraft and another hundred thousand troops. ....
Would these numbers have applied in December 1941? Had this quantity of men and material been allocated to defense of the homeland in 1941?
A look at John Ellis 'Brute Force' gives access to a couple charts showing the ramp up of the Allied bombing 1940-45. From those its fairly clear the threat from Allied bombers did not emerge until 1943. While that threat might be anticipated in 1942 the actual damage to industry was in gross terms negligible. The number of sorties and tonnage of bombs dropped was flat out insignificant in comparison to 1944. That is the large scale diversion of men, weapons, ammunition, fuel, to air defense was not of serious strategic effect until 1943 at the earliest, & then in the later half. The effect Speer is referring to primarily occurs in the las 24 months of the war, after Germany had effectively lost the war.
Precisely how the resources diverted to air defense would be reallocated is a open question. The reflexive notion is more AAA on the battle front & more AT guns are possible. Transportation is problematic as the anti air units in Germany were depending on third rate automotive transport, horses, and the dense railway system. That does not translate directly into mobility on the battle front in Africa, Italy or the eastern front. Manpower requires a evaluation o the men who served in the FLAK units. Underage boys & overaged men do not mean a 1-1 increase in soldiers on the battle front. While immense amounts of ammunition could be added to production for the field artillery such returns to the problem of transportation. The transportation campaigns of 1944. such as Op STRANGLE, left much of the ammunition sent overrun in rail side dumps, or destroyed by tactical and operational level bombing, never reaching the battle front.
Getting back to the OP, my take is 'Shock and Awe' air attacks were effective where morale was already endangered, i.e.: air attacks on Soviet cities like Minsk in late June. Tho relatively light compared to Warsaw, Rotterdam, Dunkirk, Coventry, they induced panic among a already nervous population & military service support. Belgrade a few weeks earlier should be examined for this effect. Where morale was sound anti morale effects were not close to what was expected.