- The messaging (in Spain but looks similar everywhere) has been that you should wear one if you are sick or, more importantly here, if you are at risk. This is a clear indication that they do help protect against being infected. This should have prevented everyone from harassing anyone wearing one ("they must be a risk group"). The fact that people did that is indication that people are not acting responsibly.
I personally hate being told something that is patently false, but I totally understand that, collectively, we need to be lied to for our own protection, because collectively we become a bunch of idiots.