> These sorts of lies are usually covered under existing fraud laws.
In those cases the laws dealing with fraud are still imposing a restriction on what people are allowed to say. Same with trademark and copyright laws. It's a good thing that companies aren't allowed to simply lie about having a UL certification for example.
> These sorts of situations are special because all parties agree on the rules at the start of the transaction
True, but only depending on the situation and what you consider to be a transaction. If a law is passed that makes it illegal to offend someone on twitter, anyone who uses twitter "agreed to the rules" too right? You don't always have a choice. If you give false information to police for example you haven't agreed to anything explicitly but they'll still come after you if they find out.
> I'd be fine abolishing such laws
I don't think you find broad support for that.
> Companies that didn't list their ingredients would probably lose significant business
You might think that, but history shows you'd be wrong. Gerber and Beech-Nut sold baby food that contained dangerous levels of arsenic mercury and lead. DuPont knowingly poisoned people while trying to hide that fact from authorities. Johnson & Johnson also lied and hid their knowledge that their product would harm their customers. Lenovo has repeatedly shipped malware infested systems to consumers which opened them up to everything from privacy leaks to remote code execution. None of those companies went out of business. You couldn't count the number of companies who are currently, and/or have previously and often repeatedly caused harm to their customers yet continue to operate successfully. Even when the consequences were deaths, including the deaths of children. "Voting with our wallets" is a proven failure as a means to regulate the dangerous and harmful actions of corporations.
The "fire in a crowded theater" example still holds. It wasn't overturned as much as it was refined to limit its use to what it was originally intended for because it was being abused. The risk of abuse is always present. We need to be careful to keep an eye on every case where freedom of speech is restricted to make sure it was appropriate, but just because someone can misuse something to violate our rights doesn't mean that thing shouldn't exist. Nearly every law or power police and government have are at risk of being abused. The answer isn't anarchy but oversight.