"they should still have that choice as they cannot choose what happens with their union dues"

This isn't true.

"far too many unions spend inordinate amounts of money on political activities instead of their own membership"

If you believe that, then start getting involved in your union's leadership and change it.

" then top it off with all the bureaucratic bloat and high paid leadership"

As opposed to the leanness and crappily paid leadership of the company?