I would respond to this with the energy connection, showing how promises to pay, especially those with interest, are also are promises to destroy the environment.

But I might be diverting from the moral argument. It seems to me there is another antidote, besides setting up an official law to prohibit usury (How would we ever trust lawmakers to never be bribed into changing the laws back again in the future? The lawmakers themselves are often renters and usurers. In a way, many feel trapped into practicing it, in order to compete, just like anyone else. There is no longer functioning law, it seems to me, everyone is on the treadmill.)

The other antidote I would suggest might not be palatable to many people, and I am not recommending this to anyone, but is a technical option, with maybe physical risk, and that is to sign the unfair agreements anyway, but with not an ounce of intention to honor them, with a clear conscience, knowing that unfair agreements are just something used by folk trying to rip us off, if we are happy to oblige.

If everyone did this, usury would soon go out of fashion, I believe, given that we now live in a non-zero sum world, there is no longer any argument for those with wealth to claim that they are giving some of it away, when they give to others, more comes to replace what is given almost instantly, especially for those who have lots already, the capital of Earth is physically expanding, since we started using solar energy (Another mathematical and physical fact!), so it is now easier for them to just write of their losses and move onto another sucker.