That ain't a choosing beggar example... The term stands for someone who rejects something that can be of use that's offered to them, over anything else that can serve the same purpose. Human shit would do more harm than good, so the beggar actually didn't receive an offer, but a cruel joke. Yours is the same case of Christ, who rejected vinegar while being crucified and thirsty: it was a terribly cruel joke.
A good example of choosing beggar is someone who asks for a watch, is offered a Casio, then rejects it because he wanted an Omega. Since
Succubus Hunter was kind enough to provide the link of the ChoosingBeggars subreddit, you might as well check the definition of choosing beggar there (though I disagree with the Nintendo/Xbox example; if I want a Nintendo to play any Zelda game, a Xbox doesn't serve me any use because afaik all Zelda's are Nintendo exclusive, save for Breath of the Wild which is also available for PC).