You may have seen the video of the family thrown off a United Airlines airplane because the 2-year-old daughter would not wear a mask. Though the family wore masks and the father promised to cover his daughter's face with a mask that he placed on her face, it made no difference. Though the child was completely asymptomatic, and though it is exceedingly rare for a child to transmit COVID-19 to an adult -- that is why Sweden kept its schools open all spring and summer, with its students not wearing masks -- the airline had its orders, and the flight...