They will just give you a blank stare. You simply cannot influence someone by suddenly ranting.

They will need to be told by the TV that masks don't work.

Approach them with caution, like genuine concern, and tell them they have something on their mask.

When they exclaim, "What is it?"

Tell them "The biggest fuckin' pussy I've ever seen."

/micdrop

Smiling, laughing, and in extreme cases, whistling are all good weapons. In warm weather, ostentatiously sniffing flowers, or eating ice cream cones are also good.

Logic via spoken language will work, but it's very slow for some. I trip on the folks who wear masks while walking unmasked dogs. I think posters of how dogs can spread covid (remember those articles?) would be funny.

Just talk to them as you would to anyone, try to be engaging and occasionally say "What?" so they have to repeat, eventually say "it's really hard to understand people through a mask." That's a fact no one can argue and isn't personal to them. If they take up that line keep it impersonal! Talk about the loneliness and disruption caused by "mitigation" measures. You don't know what's going on with strangers. Much more likely that you harden their attitude by attacking their choice, than that you change their mind. The best you can do is make them think about the negative consequences of masks.

If you wear glasses or are close to a window, ask them to fog it up with their mask on, then explain that those water droplets are 70 times larger than the virus. Watch them short circuit.

They know.

i do tell them, i tell them to take it off!!

nah don't be a fuckhead dude