A friend detests the idea of warehouse clubs (Sam’s or Costco in the U.S., for example) checking receipts as he, the customer, walks out the door because he takes it as being under the assumption that he is a common criminal.
Some warehouse stores may treat you that way, making you prove innocence with your receipt. But don't take it as given that this will happen. The Sam's I've been to spends about 2-3 seconds 'checking' receipts. They are very clearly just acting as greeters, not inquisitors.
they can't force you to participate in the receipt checking, you can refuse, and you are free to leave. Because those places are clubs, they can take your membership away and deny you entry in the future, but once you pay for something, it's yours, and they can't search you or your belongings against your will; unless they wish to make an allegation that they saw you steal something, in which case they can tell that to a police officer.