I can't say I see the relevance of whether the do-gooder personally needed or was entitled to the space.
When I watch the video, what I see is the do-gooder talking and gesticulating to a closed car window. Then I see a woman engage him--not by ignoring him or cracking a car window, which would be ordinary--but by getting out of the car and approaching him. At the same time, I see the hulk come out of the store unseen and stride toward the do-gooder.
Compounding the riskiness of the situation, instead of introducing himself and asking if there is a problem--which would be the normal thing to do, to avoid misunderstanding or danger to anyone--the hulk attacks the do-gooder from the side and sends him flying to the ground.
Now, if the hulk had then jumped into the car and the couple had simply driven away, you could argue that the hulk was afraid for his woman's safety and was trying to fend off any danger from the stranger.
But no. After he knocks the guy to the ground, he stands over him and puts his hand on his hip. Regardless of whether he's reaching for a gun or preparing to smack the do-gooder, the hulk is obviously not done. As the initiator of violent action, that was his fatal mistake.
From the do-gooder's point of view, he's been confronted by the one person he knew he was talking to--the woman--who has opened the car door and is now heading for him. Then from another direction, he is blindsided shoved violently to the pavement by a man the size of a bear who is now leaning over him.
At this point, I can't conceivably hold the do-gooder, who has to be seeing stars from full-body impact on the pavement, responsible for discerning the minute shifts of the hulk's feet or his intentions. The attacker in this situation is still in his face.
Bye, hulk. Too bad, too stupid. If you really found the old guy so scary when you saw him talking at your woman, and you couldn't bring yourself, at 275 pounds or whatever, to take over and defuse the situation with a smile, you could have called the cops or just packed your family in the car and left without a word. You didn't. Sometimes, annoying old do-gooders are carrying an equalizer.
Any detail gleaned about either the event itself or the players can provide perhaps important context.
E.g., now I hear that this guy was a busy-body constantly harassing people about missteps with handicap zones. Like a cop who feels the power and likes rubbing it in. Not that these people were OK being in the space, but the point is it sounds like he tends to be pushy and perhaps a bit of a power-hungry do-gooder.
Ipso facto, his trigger finger may be in question.