A cusory web search turns up indie bookstores, restaurants, literary publishers, community groups of various sorts, etc in Buffalo, Cleveland, Detroit that embrace the term "rust belt". I didn't easily find similar results for Pittsburgh, so maybe yinz do have a different take on it. But please don't assume others intend "rust belt" as a pejorative, and please consider recognizing that as it's not widely used pejoratively, you may have limited success convincing others to stop using it.