As a soldier I have a very special take on public sector unions.
Once the War for Independence was won Congress had a problem, they couldn't pay the Army a few years of back pay. So they simply put the whole Army on furlough save 40 Artillerymen and never called the rest back. In the Great Depression when WWI vets were attacked by their active duty comrades in the "Bonus March Riots."
My paycheck comes from the taxpayers (although more likely from China). If the public doesn't pay me then I don't have a job working for the public. I could not be like the Revolutionary War soldier who could go two years without pay, my family would starve while I was playing soldier. So if the time comes when a Reduction In Force (RIF) sends me packing then so be it, I'll find some job somewhere. I've been a janitor and know that I can at least fall back on that.
Soldiers don't have collective bargaining rights, nor should we. But neither should Police, Firefighters, or EMTs. In the end the only people who put anything into the economy are farmers and miners. Everyone else simply adds value to base products. I know my place in the economic scale of things and have no right to demand more than is in my contract that I signed with my own hand of my own free will.