The reason people say there are no such things as a bad or stupid questions is twofold: one is to encourage people to ask questions without worrying whether the question is 'good enough', the other is that the worst questions can be teaching opportunites. It is not literally true that all questions are not bad or stupid.
Thanks for providing the example of a loaded question. If the answer is 'yes', fine. If the answer is 'no' it could mean you smoke a medium amount of pot, a small amount of pot, or no pot. It's a valid follow-up question to the question: 'do you smoke pot' if the answer was 'yes'. Otherwise, that question can be described as 'loaded', 'bad', or 'stupid' depending on the intent of the questioner in asking it. It would definitely be loaded if you reported, based on my answer of 'no', that I don't smoke a lot of pot...it implies I smoke some pot, just not a lot. Otherwise, it's bad or stupid because you failed to consider that a 'no' answer wouldn't give you much substantial information or that a person would reasonably consider it a loaded question and would have a reason to consider you are not asking questions in good faith.