For one thing, you can run something like a credit union and have interest without it being usury. Ultimately, no one is profiting off the lending. The money that borrowers pay in is paid out to savers. For instance, the guy who is working and paying off a house is funding the expenses of a retiree. This is no sin.

You can say the difference is sophistry, but there are a couple of key points here. One: No fractional reserve. No inherent inflation just because you do lending. No funny money. Two: no government. The government no longer dictates how much a bank can lend. No Fed depositing checks in banks drawn on nothing. To me, the real sin is the divorcing of currency from value and from labor. This leads inexorably to massive inequality.