In this context, "If you don't know then you don't 'need' to know" is surely a parody of the bar room scene from
Lock, Stock and Two Smoking Barrels when Barry 'The Baptist' is briefing the two 'f****** Northern Monkeys' about the forthcoming robbery:
Gary: "So who's the Guv? Who we doing this for?"
Barry 'The Baptist': "You're doing it for me is all you need to know. You know because you need to know."
Gary: "I see, one of those `on a need to know' basis things, like in James Bond films?"
Barry 'The Baptist': "Careful, remember who's giving you this job. Right, I'm off. Call me when you're done. Ta-da."