The test is incomplete as far as determining base morality. If I carefully leave my shopping cart in between the horizontal lines of the parking lot in a way that does not affect parking, I make shopping just a little bit easier for the next person to arrive in my space. Or I could also leave the shopping cart by the entrance, where an employee doing returns or someone walking in could grab it. There's also the flip side, carelessly leaving it in a parking space which is much worse than simply not returning it. It can cause potential accidents and makes no one happy.

The real litmus test regarding a shopping cart is simple

Do they call it a "buggy"? And if they call it a "buggy" and you kindly educate them as to how incorrect but also obnoxious this specific southernism is, do they accept it gracefully? Buggy isn't even a good southernism, like "bless your heart" or "y'all" It's like insisting every soda is coke and confusing waiters and fast food employees everywhere asking for a coke when you do not even like Coke. Just say you want Dr Pepper or Sprite and make this easier for everyone.