The problem with laws is you need people to enforce them.
The problem with law enforcement is you need people to pay them and tell them what laws to enforce.
The problem with lawmakers is you need some means to determine who gets to make the laws.
The answer is the guy with more guns and pointy sticks. The guy with more guns gets to tell you that while you’re in his land, whatever land it is, you’re going to give him money or goods.
Social contract theory mitigates this to a degree, by specifying the method by which you select who the guy with the most guns is. Sometimes it’s more than one guy. Sometimes it is a lot of them, and they all counterbalance each other, but it doesn’t take away from the fact that what keeps them in power is a piece of paper and all the guns they’ll ever need to back up what it says on the paper. Everything else is norms and traditions and processes. This is power.
The problem with social contract theory is that the contract can say anything. You just need enough people with enough guns to agree that this contract serves their interests enough.
Well the US Constitution wasn’t written in a vacuum. It was written by, largely, Englishmen and some other Northern Europeans subject largely to English rule. They already had values and cultural norms and traditions, they just needed the document. Well they had one already, several actually, the Articles of Confederation and the Constitutions of every State. The Articles were not doing the job of serving the interests of the people, in the view of the framers and Madison in particular, and they swapped it out.
Now go read Article I. Examine the structure. There’s a selection process, and there’s minutia about procedure, and there are limitations. The Article I branch is Congress, it is the supreme authority of the government, not coequal with the Presidency or SCOTUS, you were lied to about that, but above them. If Congress were one guy and could speak with one voice, it could do almost anything, impeach and remove the President, any sitting Judge, any Officer of the government, amend the Constitution, and declare war at will.
These are very good reasons why Congress isn’t one voice, and it is many.
Now to get back to what you were saying, the problem with with laws against things like “broadcasting lies” is you don’t know that they will be applied sensibly. The more laws you have to begin with, then more rope you have to hang the citizenry.
The First Amendment, and for that matter the Second and Third, the reason they are as ironclad as they are is specifically to prevent abuses by the Federal Government. It was to appease the faction at the time known as the Anti-Federalists who felt, rightly in my opinion, is that the more guns you give the Federal Government, the more potential abuses for power because there will be (have been and are) who will attempt to co-opt the Federal Government to wield those guns.
Congress doesn’t need the power to determine what is a lie and what isn’t. You don’t need laws to punish liars. If you have faith in sensible systems, then the system you want to have faith in is the people. If you don’t have that, then you can’t have faith in Congress.