If SteveVickRepoboy had been taken to Germany when he was 9 years old, he would, like most German youth at the time, have been indoctrinated with Nazi ideology and pressured to belong to Hitler's Youth organization (wear uniforms, attend rallies and be militarized). By 15 he would almost certainly have considered himself a German and in the dying days of the war possibly fought (without given an option) as a brave, dedicated soldier for Hitler Jugend against the allied forces in France. He would not have been a traitor to England even when throwing a grenade at allied troops. It would have been what he had been brainwashed for, trained and believed he had to do. His actions would have been that of a child soldier - just like Khadr. 
SteveR was not taken from his home in the UK to a foreign land when he was 9 and indoctrinated in an evil cause. There lies the difference. This is a case of apples and oranges. 
See also Lt-Gen. R.Allaire's comments in G&M.