I don't find what you're saying offensive. I just find it ill-informed. Give us a specific example or two and we can discuss.
Your first one, Waltham, is pretty clearly middle class. I still can't figure out if you think Waltham is upscale or poor or what. Which is it?
I think you have a misperception of the area, and I don't think the term "middle class" is subjective at all.
How about we go with towns whose median income is somewhere between 80% and 120% of Greater Boston median income. I bet we could find that data pretty easily. I'd do it but I don't...
Revere, Medford, Malden, Everett, Winthrop, Somerville, East Boston, South Boston, Hyde Park, West Roxbury, much of Dorchester, Brighton, Quincy, Hull, Watertown, Waltham, Framingham, Natick etc. etc. etc...