It's a joke guy dont get too serious, nowhere in your meme is directly talking about masks.
I'm making fun of the fact that because she's wearing a mask , this has (i am claiming) supposedly caused you to believe that she is a left wing rioter.
So, me claiming you are a Maskist is me screwing around like a lefty making up tags/ names for people who disagree with me. Maskists are like racists but they are anti-mask wearing (you maybe pro mask idk) and therefore those who are Maskists practice maskism.