I don't think pain is universally bad. Many people enjoy pain in small doses; some even enjoy it in large doses. I think the key aspects to "bad pain" are when pain is non-consensual, when pain persists past usefulness, and when pain breaks us.

Consent is mentioned because plenty of people do invite some amount of pain in to their life willingly, and I think most utilitarian analysis would still conclude that being a CIPA patient is not a positive.

To persisting: It's useful to know that my leg hurts; it's not useful to have to endure the pain for miles as I hike back to camp on a cut foot.

To breaking: I know of no one who values being tortured until their psyche breaks, until their sense of self just collapses under the weight of it; as far as humans have universal values, that one actually seems pretty high on the list.