Hanging up now...

Why does our son always hang up on us when he doesn't like what he has to say? He has done that twice to me today and over very reasonable questions...I think. I try to only say 'no' to things that I have a backup for. My sister and I have talked about this often and I do not like saying no without a reason why. Kids like mine often require you to say no often anyway b/c he is asking the same question over and over and over and usually it's the same answer...A big NO question we get is: Can I eat dinner in the family room? 'No', "why?" 'Because we eat dinner as a family.' This is the easy answer. The long answer to that question is because both daddy and I ate with our parents every single night and it is something that we do. He isn't interested in hearing the many studies that back up why it's good for children to eat dinner with their parents and share their day, even if it is for 7 minutes. I just hate saying no, no, no, all day long. But - I don't like getting hung up on either just because I have executed this g-d given right to say it every once in a while. So there has to be a happy medium here. I haven't found where yet. If anyone has, do let me know.