I decided a long time ago that staying on good terms with management was just as important as anything else in the workplace.  I work hard at my job, and I work hard at building relationships with my managers, which is just as important IMO.  Work is just a place I go for X number of hours every week to make money for the important things in my life, so I just let the petty annoyances of my job roll off my back.  You are absolutely right about supervisors not siding against *their* supervisors.  It ain't gonna happen, period.  Management is a country club, and the help isn't allowed inside.

  Sometimes, it takes an incident like this to reassess, reflect and make a change in life, no matter your age. 
Take your experiences and see how much you can contribute in another profession or field or company and begin to market yourself. 
Your situation is one of the reasons why I have my own consultanting business after years of working for others but it has always been a goal of mine to have my own business so much of my 'career' was spent establishing a reputable foundation.  It's alot of work (net working), long hours at first but my personality is such that I am intense, but disciplined, positive, realistic, fair, reasonable, honest and have learned to glean constructive criticism from others that promote positive productive results in my work. I am not one that settles for just 'going through the motions', and at 51, I still seek adventures and new opportunities so obviously, it's up to individual insights and determination.  There will be times when you need to just walk away. 
I wish you the best!!

Sorry to hear about this Brother...down in Texas we have the Texas Work Force that can go to bat for you in cases like this. Have you checked on something like this?
Best of Luck on this issue