The value of bonds and their interest can be paid back in numerous ways that have nothing to do with taxes. They can even be defaulted on and not paid back period.
Municipal Bonds are NOT guaranteed and they can default on them so there is no direct tie of taxes to these bonds. They are only as good as the credit worthiness of who issuing them.
So before you guys continue spouting off about something you obviously have no clue about, do a little research.