Ok, so isn't it also common courtesy to leave a note with a number if you are going to leave your vehicle unattended? Two wrongs don't make a right, but if the vehicle is charged or nearly so, and I am in true need of a charge, I'm unplugging. and you know what, if I leave my vehicle unattended and it's done charging and someone needs a charge, I'd fully expect them to unplug me too.
All this absolutism about "never" unplug is just crazy. 99% of us couldn't care less if it is done respectfully, a note is left, and the courtesy to assure that we are done or nearly done charging before unplugging.
Okay, IF the OP had reached a full charge, MAYBE.
But simply believing the original car was fully charged does not make it so.
The offending party had no way to "KNOW" if the other car was fully charged or not.
As stated earlier, the OP's car was only 50% charged when he was unplugged.
That is the crux of the matter.
All the "assumptions" are what get people in a heap of trouble.
Since the OP left his car, he could have left a note on his dash with a telephone and the time he left.
Taking your logic one stop further however, the offending party should have left TWO notes.
One, apologizing profusely on the OP's car: "I am extremely sorry. I hope your car was fully charged and I removed the plug so I could begin charging. I hope I have not inconvenienced you"
That way he takes responsibility for his actions.
A second note on HIS dash with HIS telephone number and time he started his charge.
And in doing so, he also opens the line of communication in case he had wronged another human being.
Otherwise any other (3rd or 4th...) car could come up and
do the same thing to him: unplug the NY car and begin a third car's charging.
And the cycle repeats itself
ad nauseam.
Do NO harm.
Treat others with the same regard as to how you would like to be treated.
Treat everyone well, and there are no disagreements.
Start bending the rules in a selfish manner for your own benefit and to the detriment of others, and the Whole World resorts back to being like the Old West.