Union when they were initially started were there to protect workforce from harsh unfair practices.
Conditions such as were prevalent in those times no longer apply, in many instances Legislation protects workforce.
Unions nowadays are little more than a form of Mafia Protection racket.
If they are permitted to carry sway over otherwise successful businesses, all that will happen is that those businesses will eiither close down or move overseas.
The only other option is for some Corrupt Government to step in and take over that business and install Union as management, hey guess what, no outrageous demands are made of that business again.
What I have described is Communism, compulsory takeover of businesses deemed to important to be allowed to fail.
Of course your response would be that this cannot happen in the USA.
My response would be look at Chrysler and GM.