This is absolutely wrong: you cannot have a proper argument if you're ready to change your mind at the first sign of challenge. You "win" an argument if you convince a crowd of your position, challenged by an antagonist. You "change" your strategy, maybe your core ideas after the argument, slowly and silently, after reflection.

For instance if you debate, I don't know, the virtue of legalizing illegal immigrants. One would take the position that if they didn't obey the law in the first place, why reward them: they might never care for the law if disobedience is followed by reward, and the rest of society might follow too. The antagonist would argue to be pragmatic, we need labor, they're already there, they disobeyed the law to help their families not to steal from anyone. Both points are valid, both people are right, none of them can "win" in the heat of a debate - but their arguments might move the crowd listening maybe, and they can use various tricks to this effect (humor etc), to obtain a positive vote at the end.

Both opponents, after the debate and seeing the result on the crowd, will adapt their arguments for next time, or maybe shift a little if they were shown something surprising, but after a lot of further debates with further opponents. And fundamentally, a legal fundamentalist cannot be transformed into a pragmatic economist overnight, or over a lifetime quite often.