It's interesting isn't it, a person wishing to be helpful to others by creating more parking space, but doing it in a rude manner. What a dick. It's good you found the courage to say something, although I still have to urge caution as you never know how they'll react.

I had a similar case. I'd pulled into a carpark area with at 7am to get a take away coffee. There was maybe 10 cars in there out of the 200 carpark spaces available, all scarttered around. I pulled into a space right in front of the cafe, designated parents with prams and exited my vehicle.

A guy of about my age, someone who was a regular at the cafe and I'd seen many times before, said to me, you shouldn't be so rude and should leave that park for parents unloading prams and children.

I walked up to him, looked around the almost empty carpark then back at him then shook my head. I didn't say anything, my look said it all. He shrunk a little and I went in to get my coffee then drove away. The whole time I was waiting for my coffee (about 4 minutes) I stared at him with a face that sort of said, I will tear your face off if you speak again. He tried not to look, but couldn't help it and there I was, glaring at him. From that day on, he never uttered a peep, and didn't look at me.

Had it been later in the day, and busier, I wouldn't have parked there but at that time of day and with only a few cars in the carpark I didn't see the issue. He thought he was doing the right thing, but hadn't taken stock of the situation. He read the sign, saw me park there and thought to chastise me. It didn't go so well for him.