Wanted to elaborate on what I said earlier.
DS7 has been argumentative for as long as I remember. Nothing pushes my buttons faster than "the tone", so I've had to learn to handle it calmly. In recent years, the behaviour has morphed into sarcasm and biting humour wrapped in a cheeky grin, which I take as his way of moulding it into something more acceptable. 'Tis good! (A lot of you must have seen this condition, no?)
Last weekend we went to a cafe that, from the outside, seemed unlikely that they would serve a full scale breakfast. In an effort to be polite (and I agree what I said was redundant!), I asked the greeting staff, "Do you serve breakfast?" From below me, a voice said in a nasally twang, "Whaddya think they're eating? Dinner?"