I can understand why they've overreacted, but it is definitely an overreaction. If he says he just took off his mask to have the photo taken, a private warning not to do that again would have sufficed. He's taking more risks at work, so you can see why it's ridiculous from his perspective. Masks are only even shown to be helpful to prevent you spreading the virus if you have it yourself, and he's being constantly tested so he knows he doesn't.
Storm in a teacup, for me. Let me know when it's a sex party with hookers and then we can get morally outraged.