If you need to ask a question on mass genocide, well you need your head looked at. The questions that don't need to be answered are the ones that we all should know are off limits. Its not okay to do certain things, and its why sacrifices went out with the dark ages.
It's good to always wonder about the world around us. It's good for scientists to try to find out what makes things tick. But, that being said, there are still some questions that we don't really need to go around asking people in polite company, such as, just as a random example, how much money they make. Our curiosity should be tempered with common sense.
There is such a thing as questions that do not need to be asked. People often actually already know the answers to these questions in their own mind. Some people just like to be overly-re-assured. Other people just want to rub it in when they are right and the other party is wrong.
No, questions are always worthy of discussion. There are many questions that make people very uncomfortable. However, that does not mean they should remain unspoken. Just ask Dan Savage, who spends his days answering questions about sex. While these questions make some people uncomfortable, there is a huge audience for "Savage Love," a weekly column in which he responds to readers' questions about sex.
I do often get a little irritated at how some questions already have an answer, but people ask them anyway.I have to reel myself in and realize that some people are just out of the loop on certain things. I probably ask a lot of questions that seem obvious to other people too. That is why the only dumb question is the one that is not asked.