The legal tender law targets the lender. It grants to debtors a right to repay a debt in dollars. In practice, this means that if you lend gold, the debtor gets a free put option at your expense. If the gold price rises, he can repay in dollars. If it falls, of course he will be happy to repay in gold. It’s a rotten deal for the lender.
The relationship between lender and borrower is mutually beneficial, or else it would not exist. The parties are exchanging wealth and income, creating new wealth and new income in the process. The government is displeased by this happy marriage, and busts it up by sticking a gun in the lender’s face. His right to expect his partner to honor a signed agreement is violated.
Because no lender will lend gold under such circumstances, gold is relegated to hoarding and speculation only.
This strikes a blow to savers, because the best way to save is to lend and earn interest.
Savers are forced to choose between hoarding gold, getting no yield, or holding dollars and getting whatever yield crumbs are dropped by the Fed.