Sometimes, if I'm in a snarky mood, I'll ask someone where they obtained their degree in endocrinology. That usually shuts them up. If I'm feeling a little more patient, I will try to explain to them what I'm doing and why I have to do it. For example, in the situation you describe, I would explain what could happen if the amount of carbs is miscalculated. And how, back in the days before we did carb counting, BGs would swing wildly from highs and lows, thereby leading to really bad complications later in life. I would explain how what you're doing now is helping your daughter not only feel better in the moment (because her BGs are more stable) but also helping ensure she stays healthy for the long haul.
Just because he's a doctor means nothing. I have actually encountered more ignorance among medical professionals (who are largely accustomed to seeing and treating T2 diabetes) than I have in the general public. And this really, really scares me. I have a friend who is a GP and she frequently asks ME questions about dealing with patients who have diabetes. She explained that in med school there is very little attention devoted to diabetes in general, and even then most of it focuses on T2 diabetes. Unless a doc or medical professional is an endocrinologist, I pretty much expect they know next to nothing about T1.