While this kid's beliefs are probably skewed by his anger, he does bring up the fact that the Air Force as a stand alone service, much like the Luftwaffe, creates barriers of military capability. You only have to ask yourself about the success of German Naval aviation during WWII. The Germans built a couple of carriers, did some workups, and then realized that their AF pilots couldn't get the Navy's ships to go where they wanted. Hence, there was no large scale german carrier-borne aviation during WWII. The Luftwaffe also had its own army, because if the AF was going to have to carry paratroopers, then by god, the troops they were dropping would have to be AF troops, creating another manpower mismanagement. I think anyone can see that for these, and many other reasons, the idea of an independent AF will compromise the abilities of your other services if the AF is operating in its own self interest.
Think that those examples only apply to germany's AF? If you look closer into the history of the AAF pre 1947, you will find a good deal of its "heroes" actually did their best to stick it to the Army and Navy. Billy Mitchell used the press to leverage the politicians to throw more money at the air forces which led to his court marshall. Hap Arnold fought to build fighters without hardpoints so he could secure more money for aviation persuits without having to allocate his resources to help the Army on the ground. After the formation of the AF and into the missle age, the Navy's budgeting was crushed while the AF kept building more planes and missles. The only thing that kept the Navy from drifting into oblivion was the MC's preformance in Korea, the Cuban missle Crisis, and the Navy's fast response to world events that couldn't be remedied with a ICBM. Even with all of the money that the AF got for its missle program, the navy STILL led the way with its polaris and posideon solid state missles, something it took the AF a while to adopt.
Today things aren't so bad because everything is about jointness. I still think that we should understand that an independent airforce has limitations, albiet different from the limitations it would have had it stood with the Army.