I am pretty sure they were responding to the "lack of trust" point raised by the parent, not the crime itself.

Their point was that they aren't worried / don't lose trust in the bank if it gets robbed. Rather, the money is guaranteed, so they retain confidence in the bank even if it loses a lot of many due to a particularly successful robbery. Because they'll still get their deposit back.

This is 100% what the FDIC and NCUA are about: ensuring continued consumer confidence in their banks.