I don't see how even Amazon can try to kill the competition in a market that huge, regardless of price or convenience.
So I assume you wrote this after picking up groceries from your locally owned grocery store? Because you still have one - it didn't collapse due to a Walmart coming to town?
Most of us have a solid example of what driving a grocery store out of business looks like, though.
But I think there's a case to be made that everything is a permanent debate. Let me just paste a quick wall of text here on the topic...
Sorry. Just trying to make you laugh. I will see myself out.