You never know when you’re going to be the “lucky one” and sit next to a person who wants to chat during the entire seven-hour flight or someone who can’t stop coughing and sneezing.
Passengers should understand that an airplane is a public space. All courtesy rules apply. Would you relieve yourself on the street if there was a restroom nearby? Or would you leave your newborn child on the floor or in the overhead bin? Shockingly, or maybe not so much, many people think this is acceptable.
Don’t be one of “those” people, but feel free to take a picture of them. They deserve to get the bad credit and, maybe, get discouraged from acting badly. After all, do you want a half-naked person sitting next to you? It happens more often than you might think.