Nobody I know, me included, can stand all truths, inquiries, arguments, and challenges any time day or night. There are, from time to time things we’d rather not talk about and times when someone brings up these unwelcome topics. We find ourselves engaged in a dispute and wanting to back out, in effect to say “no contest” without surrendering or claiming victory.
In contests the points matter. A clean extrication would have no bearing on the score. It’s hard to say a clean “no contest,” that doesn’t mean “You win” or “I win.” Your challenger is still in the contest trying for points, and maybe you are too even though you claim to be exiting it.
“Let’s talk about this some other time, shall we?” can be said with a subtle sneer, implying that the challenger is out of line. A sighed, “Please, not now” can imply that the challenger is abusing you. “Whatever,” implies that your challenger is an idiot. Even just changing the subject can be patronizing.
“My, aren’t we touchy!” the challenger grins, glorying in the false sense that he’s not touchy about anything. Even his silent compliance can be pregnant with scoring implications.
It would be nice if, among friends, we could pre-established a score-neutral way to say “no contest,” perhaps borrowed from the rules of other contests. In courts, pleading no contest implies surrender. In wrestling “tapping out” or saying “uncle” gives the score to your opponent.
The best analogy is “safe words” is sexual experimentation. Partners, open to challenges, but respectful of their mutual limits, pre-designate a word that means “OK, enough challenge for now.” We could use that conversationally, safe words that don’t mean you’re the wimp or a winner.