If a motorcyclist has an accident and injures himself to the point where he is a vegetable, you and I get to pay to take care of him for he rest of his life. This being the case, in most states we insist he wear a helmet as it reduces the odds of our being saddled with his lifetime care.
Similarly, if a healthy young person elects not to buy health insurance and subsequently becomes very ill, once again we will pay his bills. Our society is uncomfortable with the idea of allowing that improvident person to die because he or she has no insurance nor cash with which to pay their bills.
If we are unwilling to allow persons without means to sicken and die without care, then we must require them to purchase health insurance if at all possible. Not to do so is to encounter "adverse selection." "Adverse selection" occurs when only the people likely to get very sick buy insurance. If that happens, the premiums will be horrendous.
If requiring healthy young people to buy health insurance is a tax increase, so be it. In this case, the old business professor's knowledge of insurance principles outweighs the old conservative's desire not to raise taxes or to interfere in peoples' lives.
