Just pull out a box of those masks they sell, point to the spot on the box where it says "Does not protect you from covid-19" and just say "And yet...we are made, under threat of violence enacted upon us by the government, to wear these to protect us from Covid-19" That one has worked well for me if you do have a box handy because it's right there inked out on the box. You can let them see it with their own eyes