So, yeah, I understand it took you two hours to dig your SUV out of the snow. I get it. We all had that experience. But when you leave a chair in "your" space, that's just gauche. What you're saying to the world is this:
1. I'm selfish and I'm in this life for ME.
2. I don't trust YOU to have any manners.
3. I'm selfish so I have to reserve my precious spot.
4. I somehow own this particular chunk of CITY STREET.
5. I don't realize that I cannot reserve chunks of the CITY'S street that we all pay taxes for.
I was so tempted to park my car there and lock the chair inside with a big Sharpie note that said something like, "THANKS FOR THE CHAIR AND THE SPOT!" Maybe throw away my keys and leave it there forever. To prove a point. So, better, I explained to my child what bad manners were.

Worse, later this evening, the SUV was parked there and the chair, God bless, was in the middle of the sidewalk, blocking that one shovel-width lane where humans could walk. Guess he owns the sidewalk to and YOU CAN'T WALK THERE!