Is ionic charge just a label?
These ionic charges actually do behave as you would expect from electric charges: cations will be drawn towards the negative pole in an electrolytic cell while anions will be drawn towards the positive pole. The same feature can be observed with &alpha; and &beta; radiation (which are $\ce{^4_2He^2+}$ and electrons, respectively); these are deflected in an electric field as expected.

On a more philosophical level, the entire concept of one charge being ‘positive’ while the other is ‘negative’ is of course meaningless. We might as well have called them ‘East’ and ‘West’ charges akin to the North and South poles of a compass. The only physically observable is that the two act as opposites; two particles of like charge will repel, two of opposite will attract. Having positive and negative charges makes calculations much easier though.