Why is it correct for a Company to be forced to collect Union dues on behalf of the Union? If the Union is the true friend and advocate of the worker, the worker should be delighted to pay those dues directly, without being forced to have his/her pay reduced via the payroll withholding mechanism. I don't understand the claim by those in the Unions, public or private, that it is "Union Busting" to have the employees pay the dues directly.
Your question is logical, therefore union bosses will villify you for asking it. Union members are told how to act, how to vote and basically how to breath by the union bosses. They are robots who can't think on their own. Don't expect them to ever "cross" the hand that feeds & protects them.