Can't speak for in the US, but in Canada, government jobs are "priviledged". You won't become a millionaire, but they have great salary, usually 5 or 6 years and they reach maximum tenure. Postal workers get $50k+ per year, 6 weeks vacation, 14 sick days. All govt jobs have great benifits, pensions and usually have strong unions protecting them, slapping someone wouldn't get them in any serious trouble.
Any govt employee does far better than an equivalent job in the private sector. To me a mailman is a glorified news paper boy. When you block their mailbox, they don't deliver, when they are sick, they stay home, they never need to worry about losing customers; can you say the same about your business?
Not saying they should be treated bad, but they have a good thing and should respect others trying to make a living in more difficult circumstances.