An (unlikely) charged black hole can be described with the mass, angular momentum, charge and the thermal radiation. The reasoning behind the thermal radiation rests on the particle creation outside of the event horizon. What is the reasoning behind the escape of the electric field beyond the event horizon?
The charge of the black hole isn't actually related to whatever is inside the black hole so much as a statement about the fields surrounding the black hole. This is a static field, so there's no problem or contradiction with the fact that we can't communicate with the "inside" of the black hole.