Do please inform him that Allah Most High has declared in Surah al-Tagabun that we should *fear Him to the extent that we have capacity to do so*.
Although the paper currency is bogus fraudulent Haram and an amazingly dangerous instrument of oppression and universal slavery, we are permitted to use it until such time as we can escape from its poisonous, deadly and sinful embrace.
My own opinion is that such escape is possible only through the creation of micro-markets which use only Sunnah money and which are a part of
remotely-located Muslim Villages.