I'm not saying I don't agree the grocery store owner had a little douche-baggery going on, but we also don't know the history about his lot being used for what purposes in the past. Again......agree or not the lot is his to do with as he wishes.
Also, parking in another lot to run in and get a pizza is a little different than parking there to go get your drink on at the bar. Chances are had he parked there for a quick stop he would have been gone well before the hook got there.
Your logic has no place in here, FPD.
A 30 second stop to get a pizza is the EXACT same thing as using someone's private property for several hours to go tie one on at the bar.