Sure the world might be a better place if everyone told the truth always. But this is advice for this world, not a hypothetical one.
Besides, it's totally possible to negotiate in good faith without lying. Professional negotiators actively advise against lying because A) you might get caught B) it's harder to remember a lie than the truth later on. (This is how a lot of criminals get caught.) If someone wants to know something you don't want them to know, you don't have to answer. Tell them it's not relevant or change the topic.
If you ask me for some information that I don't want to share and I say I don't want to answer that, or it's not important, that is not lying by omission. Or lying at all. That's me protecting my privacy. Giving an incorrect or misleading answer instead would be lying.
So, lie then, is what you should do instead of lying, in order to have a good faith negotiation.
Ps a lot of corporations commit crimes. They are professional liars, they don’t lose track and when they do get caught (hardly anyone is looking), they pay a fine and do it again.“Cost of doing business” if you will. Plus your common criminal usually isn’t able to get politicians elected by contributing hundred of millions to their campaigns, etc.
There’s a big difference between lying and not revealing information that works against you.
In (American) courtroom terms it’s the difference between perjury or invoking the 5th amendment.
Some people feel obligated to provide an answer when asked a question, rather than tactfully declining to answer or changing the subject. It stems from a desire to be polite or please the other party. Ironically this desire to please or be polite leads those people to tell lies because they feel like they won’t get caught.
Skilled negotiators can be very good at identifying when someone is lying. Far more than the average person would guess. I did hundreds or thousands of interviews and after a while many lies stuck out like a sore thumb. I have no doubt that some people slipped lies past me, but most often when I had an inkling someone was lying I could confirm they were lying with some further questions or basic research online.
Once that trust is lost, everything is in question.
Maybe the point could be elaborated "never mislead".
As a parent, while I don't want my children to grow up in a shoebox, I also don't want them awash in the hedonistic filth of our day, either.
So I tell them "form follows function" and express the importance of actual marriage, not the modern variations.
It’s still better to have the principles than not have them, just keep balance in mind.
[1] for you, that is. People who don’t share your principles might not like your choices and you might be making their life difficult with your lack of balance. See religion, politics, etc.
Totally tracks
If all parties were honest then a negotiation wouldn’t need to take place.