OK, my "Excuse Me For Living" warning light is blinking.
If you were parked in the lot, you're entitled to eat in the restaurant and leave your car taking up a parking space.
You were parked on a nearby street--but you're still entitled to use your parking space for the time that you spent wherever it was you were going.
In your case you didn't stay at your destination--but you are still entitled to that parking space. You do not have to drive around looking for -yet another- parking space to eat in while your food is getting cold, etc.
I'm with your dining companion--sitting in the car while you eat is totally your right. You could sit in that parking space for *any* reason.
And it might even be more efficient (in the way that doing all your bank transactions at once instead of standing in line multiple times is more efficient, in terms of total impact on -all- other people).
I think insisting that he move the car to another parking space was unreasonable. you should have stayed put, and driven off once.
I think he was belligerent because he knew you were wrong.
You seem very determined to insist that you were right and he was wrong.
Once you take a parking space, it's yours until you leave it. You don't owe it to other people to inconvenience yourself in order to make life easier for them.
The question I asked is 'is it inconsiderate to take up a parking space that other people need/want when you don't need to be there'.
No, it is not.
And you and your xdh (and you and I) are having a difference of meaning on the term "need."
I would say you still need that parking space--because you need to eat. And that other people don't need that parking space, because there is one farther away.