I do understand your position. But this isn't like painting Cartman or a NASCAR logo on the helmet. His helmet art is indicative of the finest American emotion.
Check out US Naval aviators and USAF pilots helmets. Not exactly "uniform."
They are riding within the vehicle. I guarantee the Navy would have something to say if a pilot wanted to put a custom stars-and-stripes paint job on his F/A-18.
This isn't a matter of an authorized emblem like nose art or tail logo...it's painting the whole helmet.
Perhaps he should be allowed to do this in recognition of his service, but then it should be made a policy that allows the privilege to be earned that way. Just an entitlement to special treatment, though? No.
Some Army pilots are the same.
I know of quite a few aero-scouts that wear Stetsons with numerous DUI’s (Distinctive Unit Insignia), and other pins such as mini IFOR/SFOR crests from Bosnia, etc.