The appropriate "caring for grandma" control here is for the sick person to stay home... self quarantine... when possible. If one can't stay home, one should CHOOSE to avoid harming others WHEN SICK.

The fallacy in your opinion is it has no scientific basis. And a healthy person wearing a mask only helps the mental anxiety of the other. And, sorry, not my responsibility.

BTW, my "opinion" is backed by both scientific studies and the Constitution. What is yours backed by?