Walking too close to where someone else is camping is a simple issue of respecting or not respecting another person's "space".
I don't stand too close to a stranger. I don't sit too close to a stranger. I don't walk too close to a stranger. I don't eat too close to a stranger. I don't sleep too close to a stranger. I don't camp too close to a stranger. I don't etc. too close to a stranger.
It's called decency with regards to, and respect for, other human beings. It should be honored out in the middle of nowhere or in New York on New Year's Eve.