Caplan is 49 years old and in apparent good health. There is little risk* that COVID-19 will affect his personal health, whatever his behavior. *EDIT: little risk, relative to other risks that he already accepts, such as driving a car or drinking sugary soda.

How is it rational for him to buy and use gloves for grocery shopping, if not to reduce the risk of spreading disease to others?

I'm not sure I understand what you mean by generalizing. His behavior is to become informed about the risks and make carefully calculated, emotionally neutral decisions that balance the positive and negative consequences of his choices. I would like to see that pattern generalized. His specific choices (on restaurants, or gloves) are tailored to his individual situation and preferences, and should not be generalized.

Note that Caplan does not pretend to have all the answers. Admitting to confusion, he points out the value in relaxing behavior and restrictions to measure the risk that comes with a more open posture. A more effective and ethical approach might be paid voluntary human experimentation to improve our understanding of the risks.