Legal tender should be anything that people will accept, Myself I prefer gold or silver coins.
Taxes is a subject that I love. We have parasites voting to increase their benefits. I think only property owners should be allowed to vote on taxes for the many things which property owners are the primary supporters of such as public schools.
>>it allows him to violate contracts with impunity<<
Your evidence of this is what?
His admitted refusal to pay his mortgage using funds that are legal tender.
Of course it shouldn't.
The entire point of having legal tender is to have a standard which everyone is required to accept for the satisfaction of an obligation.
Were that not the case, then creditors could take advantage of debtors by continually changing the goalposts of what they are willing to accept to satisfy a debt.