I have seen several post stating that Bannon is a Leninist. He wants to destroy the establishment as Lenin and the Bolsheviks destroyed the old Russian establishment in the Russian civil war. Something else that Lenin and the Soviets did was to enforce communist ideology with the use of political and people's commisars in military and government organizations.
He is setting himself up as the political enforcer (commisar) on the NSC. All of the decisions made by the NSC (with Bannon on it) will have the appropriate political spin to enhance and support his and Trump's world view and agenda. This is a very dangerous development.
I am not sure how but we must get Bannon off of the NSC.