I haven't stepped foot inside a fast food joint for years, but surely the rude customers are not bad enough to warrant government advertising? We all have tough jobs. In fact, I'm willing to bet most of us with careers have a much harder time at work than McDonald's staff.
Granted, most people in these positions would be kids or others who aren't equipped to handle verbal abuse, but if this has become sort of pandemic among hospitality workers then surely the burden should rest on the company, not the customers. If the government is worried about mistreatment of retail staff, then perhaps they should force employers to kick out or refuse to serve rude customers. That's a lot more reasonable and realistic than socially engineering people to be less rude or demanding that they change.
You need to visit better venues. Or perhaps their service is a reflection of you?