What if usury isn't bad?
Rent is bad in excess. No one wants to get rid of rent. 
Business loans at interest are justifiable. Mortgages at interest are justifiable. Auto loans at interest are justifiable. People talking about a flat rate agreed to up front are creating something indistinguishable from a fixed-rate loan and that puts a burden on the creditor. 
What if there's nothing bad with loaning at interest and what's bad are exploitative loans at interest just like there can be exploitative rent or property consolidation or retail prices?