On the other hand, that 'universal rule' also necessarily stipulates that taxpayers can be absolutely steamrolled by whatever tax hikes are necessary to fulfill the bloated pension benefits that unions promise themselves.

Alas, that one 'universal rule' may finally be at risk as the California Supreme Court is currently considering a case which could determine whether taxpayers have an unlimited obligation to simply fork over whatever pension benefits are demanded of them or whether there is some "reasonableness" test that must be applied.  Here's more from VC Star:

At issue is the "California Rule," which dates to court rulings beginning in 1947. It says workers enter a contract with their employer on their first day of work, entitling them to retirement benefits that can never be diminished unless replaced with similar benefits.

It's widely accepted that retirement benefits linked to work already performed cannot be touched. But the California Rule is controversial because it prohibits even prospective changes for work the employee has not yet done.