I think I put too many negatives in that sentence. I am claiming that interest-bearing loans are the only economically rational ones (because otherwise you're taking on nonzero risk for definitely zero reward), and interest-free loans used to be widely acknowledged as the only morally justifiable ones.

Ah, you're right. It's just the sentence structure that confused me.

(I asked another question here but decided I'm having a hard time reading or composing standard written English today so, some other time!)