Did you ever see or hear of a doctor going into surgery without a mask Doctors and nurses wear masks to keep from infecting weak, sick people with germs that they, the medical people, have, and have already built immune system immunity to.

That's all that Trump was doing. He was visiting some sick and elderly service people. And he was protecting them from diseases he might have, just the way doctors and nurses do in the operating room.

Btw, if you don't trade your mask for a new one every two hours or so, your old mask becomes a haven for all kinds of bacteria and viruses that grow in the mask. Trade it in for a new one, or at least wash it, or you will be infecting a whole lot more people (yourself included) than if you hadn't worn the mask in the first place.