I would get checking receipts in the case of something more expensive like a TV or a vacuum. I think it ridiculous in the case of a jar of peanut butter or even groceries clearly already bagged and paid for. That Walmart greeter/receipt checker may not have the mental faculties to gauge the difference in scenarios. I don't think he was operating on the assumption that you were a thief, I suspect they gave him a directive to check every few people and maybe skip people with bagged stuff coming from the non-self-checkout lanes. Anyhow, I respect that you were fed up and you weren't polite about it. You weren't nasty either. The receipt checker was way out of line...over a jar of peanut butter. NTA