when it comes decency and common sense, what holds good for a public charger is also good for a private installation.. after all it is decency and common sense you are talking about - a shared critical resource that has limited availability should go to the needy first. Every heard of the phrase, 'women and children first'?
I've heard of women and children first....but that's for holding doors open, or getting into lifeboats......
Children aren't old enough to have an EV, and unless I saw the driver get out, I'm not going to assume a driver of an EV is a man or woman.
So your idiom, while well intentioned, doesn't necessarily fit neatly in this situation.
Let's try this one:
You're in a state where you're allowed to pump your own gas, so not New Jersey.
You are in a tiny "city car" with a small gas tank, and hence, short range. You come upon a gas station that is full, and you pull in behind a big SUV....
the pump is running, the driver might be in the store, what do you do?
Do you stop the SUV's pump and start pumping your little car, because in your mind, you need it more?
Do you sit around and wait for the driver to come back? Do you look for another station?
Hint: it's not ok to stop another ICE car from pumping based on your need, so why is it OK for you to determine who has more need at an EV charging station?
What if that car's owner has no power at their house because of a storm, and now they had some event where they have to travel outside of the local area, and a J1772 is their only option?
You don't always know the other person's situation, don't make assumptions. What would you say if the driver was coming back to the car and the confrontation turned physical?
While they may not be correct for assaulting you, if you were witnessed tampering with their charging, YOU might be the one explaining things to cops.
TL;DR: If you're name's not on the car note or the title, DON'T TOUCH IT.
Live by that, and you'll be ok.