Others can feel free to chime in, but to me not lying is not just a higher law of personal righteousness, but also a negative duty under law. Why? Because lying usually involves not only deliberately robbing others of correct knowledge (and establishing a falshood in its place) but also for the intent to do some harm (so that the liar is benefited). Is this not fraud? Has not a violation of their rights occurred?

If people pass on false information unknowingly then there has been no malicious intent, even though serious consequences may follow.

First of all, why the phrase “if it were known” is included here? It seems like the author tried to imply smth with that, but I fail to see what exactly.

Also, it is hard for me to see how, is somebody sells produce in the marketplace and tries to present his products in the best possible light and advertises using mispresentation, i.e. lies, why would the government have to interfere here, since it’s purely a buyer’s and seller’s business. If a seller tries to deceive a customer, it is up to the customer to make his research and stop using the services of that seller.
Of course, when it comes to a signed contract, it’s a whole different matter, yet as far as verbal agreement, I have a hard time seeing a justification for government’s intervention here.
I admit that I have a hunch that this line of reasoning is somewhat flawed. Could you please explain to me from a Libertarian point of view why should such lying be punishable by law.
Thanks in advance