Lots of folks are going to be very defensive and that's okay. It is difficult to do something so different and uncomfortable. Encouragement and empathy go a long way. It is still our communal responsibility to educate one another on how to try to behave in the current shared environment. So saying to someone "Hey it's a good start putting on that mask but I don't think you're doing yourself any favors wearing the mask like that" is tough but it costs you nothing and may help encourage them to try harder. A lot of folks will just come back with ire and malice but that's on them, you can just try to be positive and helpful. My wife is and ICU nurse so I wear a mask any time I leave the house to protect people from me, mainly.