It isn't "mere contradiction". It is a looking at what the writer is doing rhetorically and questioning the root of his argument. Again his characteristics of disease have nothing to do with our medical understanding of disease. Disease means something rather specific in the medical profession, and just throwing up a bunch of characteristics based on nothing more than he writers intuition (and with no supporting evidence) is a horrible foundation for an argument.
Most of, if not all of them have nothing to do with what disease is. He is creating a definition wholecloth through his characteristics.
disease /dis·ease/ (dĭ-zēz´) any deviation from or interruption of the normal structure or function of any body part, organ, or system that is manifested by a characteristic set of symptoms and signs and whose etiology, pathology, and prognosis may be known or unknown.
The disease characteristics is where this essay breaks down. Those don't really line up with any medical definition of disease. Seems like he redefines disease in order to deconstruct it a bit.