If anyone should get tagged for this it's the ripple developers for promoting a system which automatically treats even explicitly worthless debt as having the same value as payable-on-demand debt. Sounds like they intend to fix this - but it's hardly a new issue or one which they were unaware of.
It doesn't automatically treat any debt as having any value at all. It considers all assets as completely worthless until and unless you specifically tell it to value some particular asset.