"Grass chose to be one of those Futter was fleeing." -- Grass claims he was forcefully drafted by the SS in the last months of the war. In fact many old men and children as young as 12 were forced to fight towards the end of the war and executions of those who refused were common. Your whole argument relies on Grass's fervor to volunteer. Nonetheless I agree that Grass is a vain man and his poem is embarrassing and its contents far from reality.
from the article: The moral blindness of Gunter Grass