When some shitwit asks me why I'm not wearing a mask (which is usually every fucking day) I can tell you from experience of attempting many different tactics (appeals to logic, attempts at debate, medical excuses, pretending not to hear, pretending not to speak English, going fucking ape shit and over the top crazy, etc) -- the one with the typically quickest resolution (full cessation of interaction with said shitwit) is simply "Fuck off". Not an angry "fuck off", not an emotional "fuck off" with a raised voice, but just a rather dismissive and calm tone accompanied with direct eye contact for the moments those two short & quick syllables come out.