The issue I have with Window Cleaning isn't one of class. There are three main problems:
1) It's socially isolating.
Unlike most jobs you have very limited contact with other people. If you work with other people then they will be JW's as well. Interaction with householders is brief.
2) It offers no skill advancement
Once you have learned the skill of window cleaning you never need to learn anything else. You don't start as an apprentice cleaner, spend years learning the trade and become an expert. Also it doesn't teach any skills that can transfer to a better career. I call window cleaning the velvet trap, because you can earn decent money, but you can't escape.
3) There is no security in older age
You do not get a decent pension as a window cleaner and every year your joints get a little bit stiffer but you have to keep on working.
You may turn your window cleaning round into a successful business and start employing other JW's and eventually have an income without having to hump a ladder yourself, but in order to achieve that you have to bend the JW rules and ignore the whispering as you pursue a "materialistic" goal. So it's not the people that are the issue, it's the job itself.