I'll laugh at most people wearing a mask, but I don't if they look like they are in their 80s or may have cancer (sunken face, splotchy hair, etc). The old ones need all the help they can get. I know it may lower their oxygen intake also, but that is their choice.

I have been known to say to my wife (loud enough so a young mask wearer could hear) that she should watch out because someone that must be very sick is coming and to hold her breath. Wife gets mortified - I just get a big grin.