Bad words vs Inappropriate words

Lily has been the bad word police this week. She told me that her friend had to turn the volume off on the movie they were watching because it was saying bad words. I was assured that there were no bad words in that movie by her friends Mom. Lily told us the movie said the "s" word.......stupid.  I have always told the kids they were not allowed to say stupid. It's just not something I wanted them to call people. Just like shut up. It's just not allowed. Problem is, Lily thinks they are bad words. So Lily and I had a talk about how some words are not bad words, just inappropriate words. I hope she understood what I was talking about. I can just see her telling her teacher that some classmate said the "s" word and the poor kid gets sent to the office for saying stupid.