I've been watching 7th episode of Aldnoah Zero S2, and stumbled across a part I couldn't completely understand - なぜでもだ. If I'm understanding correctly スレイン is saying something like "Don't give me your 'why?'" or "It's none of your business" etc. However what exactly does this phrase means? Of course it's connected with previous phrase 「でも なぜ…」, however what has changed, when he rephrased it backwards?
This moment starts on 6:54.