1.5 seconds into the video I recognized exactly which lot this was. Flushing, Queens and one of the few large lots left (paid, no less) due to over-development of housing and commerce. It's such a nightmare in that area to park that I'm amazed there are so many restaurant patrons. Maybe they all take the train in. But still, people need their chinese food/groceries too, so they trek down there anyway.
And to answer the OP, absolutely not ok to hold a spot. I don't get why people would cause/start confrontations like this anyway. When the furious party "leaves" and you've "won", you're risking your property for damage later. The two times I've yelled at someone who slid into my spot, I didn't take it either.