Darvius knows full well that he's in breach of protocol by bringing light anti-armour weapons to the dinner table anyhow, especially aboard the ship. Now, if it was a case of 'negotiating' with someone, then you get to bring out the heavy guns for 'polite meetings', especially if they have a very good chance of becoming impolite.<br/><br/>(also, technically, if Darvius did attack Klaus, he could be brought up on charges of assaulting a superior officer, which in the imperium, at least, results in summary execution)