With money one party has to borrow it first and pay interest. With barter nobody is paying interest. The money lender is clearly abusing his "authority" over money by excluding it from the economy. He uses that power to charge interest and thereby render economic activity that can only cover its own costs unprofitable.

Here is an example. I sell you an apple for $1 and you sell me a banana for $1. We are both better off because I like bananas you like apples. However, if I had to borrow the money first from a bank with interest, then the trade would not be profitable. This is the real source of unemployment. Artificial minimum profitability.