It can be dehorned with thin strips of abrasive cloth operated shoe-shine style. Work up through finer grades to crocus cloth to polish it, if a polished finish is what you want? Otherwise you can stop part way up the grit grade chain where the finish texture seems to match best? The surface finish needs to match the rest of the part as closely as possible. It will obviously need refinishing in the end. You can get rolls of cloth-backed abrasive from a tool supply house or a knife making supply place.
