I think you over-reacted, and that something else is going on in your life that you are not addressing; and instead you TRANSFERRED your anger and objection onto an impersonal corporation with a real live person working for it.

>" The second time I tolerated it. I’m sad to say, I wasn’t very nice about it."

Look a little deeper. Is it the job? A family member? Disenchantment with the government?
SOME THING is up, and I rather doubt it's being asked to do something that not only IS policy, but that makes common sense.

>"On my way out the door greeter stopped me, I like him. He’s funny, lively and always smiles. He asked for my receipt while looking in my basket."

He's just doing his job. He probably likes you too (or at least....DID).
He just expected you to follow through, making his day easier, but nooooo; you had a fit.
With him; the guy you "liked". I think you need to look at a deeper problem here.

OR...just don't shop at Walmart.

PS. Do you wear your seat belt?