Here's the fundamental issue I see with the author's logic. If someone elects to not buy car insurance, yet persists to drive and then gets in an accident with me, I (or my insurance company) has legal recourse to pursue reparations from the uninsured driver. In the case of an uninsured individual who has a medical problem, I and other insured individuals often pay for the individual to get emergency medical care. Unlike the case of car insurance, I have no legal recourse to persue reparations, even though the uninsured patient is harming me (and most of you) economically.
Until someone can guarantee me that I won't be subsidizing uninsured medical patients, then I absolutely think it defensible to require everybody be insured.