How is maintaining public restrooms a "massive liability"? Surely its an inconvenience but massive liability seems a bit of a hyperbole.

The same liability exists without them.

The problem was not eliminated. If anything, the effects were amplified.

It just moved the poop mess and dirty needles from one defined space back to everywhere else. In this way, they're easier to accidentally encounter while out-and-about, and yet simultaneously harder to intentionally find and clean up.

I think this kind of result has strong resemblance to what is colloquially known as a footgun.