"Gypsy cab" is a slang term for an unlicensed taxi, and no longer has anything to do with the Romani people. It's not a term I personally use (outside a descriptive context like this), but it doesn't seem intended as an insult.

Maybe not, but wouldn't it be better to avoid antiquated ethnic slurs like "Gypsy cab" in favor of cool neutral terms like "unlicensed"?

One of the (I guess intended) effects of using an aniquated slang word is to illustrate that this is not a new problem, but that this very same problem exists for so long that it got its own well known insulting term a long time ago.

It's true, which is why I don't generally use the term myself. I was just trying to clarify the point.