A sinner is one who commits sins. John goes on further that no one begotten of God sins and that this is how to tell the children of the God apart from the children of the devil. Indeed all four versions of the gospel readily show Jesus healing people from lameness, blindness, dumbness and even casting out demons. In the fact the works of demons seem to be focussed at making people blind, lame, dumb and possessed. Any healings like these, then, are not consistent with the nature of demons.
Demons disrupt human life rather than make it whole.
Not even an angel of light would be able to feign such a healing. Some might object by stating that these were works of the Lord and only he could do these things. Yet the Lord himself said that all his faithful followers would do the things he does and even greater. Paul brought back to life the young man who fell from the window sill. Even among the fundamentalists today healing is accepted.