Take the argument to the extreme, is it OK for every employer in every industry to agree on wages and no-poach? What about on child labor? Minimum Wage? What about colluding on prices? Aren't these all the same infringement? The truth is sometimes society has to take away the rights of the few for the sake of the many. While I agree we tend to do it too often, you will be hard pressed to find many who agree with you on this matter. The fact is rules like this almost certainly make our economy more productive as a whole.
> Take the argument to the extreme, is it OK for every employer in every industry to agree on wages and no-poach?
Why isn't it? Those agreements don't restrict or infringe on the freedom of others to form different agreements, or avoid forming them.
> What about colluding on prices?
Same exact situation. Price agreements don't restrict the freedom of other parties to set prices contrary to that agreement.
> Aren't these all the same infringement?
Without getting into specifics... Yes.
> The truth is sometimes society has to take away the rights of the few for the sake of the many.
I truly commend you for your honesty about what these laws are.
> The fact is rules like this almost certainly make our economy more productive as a whole.
I don't see where that's been demonstrated here. They certainly aren't productive for the firms who are punished for, or prevented from, forming such agreements. I would argue that the fact that firms do form such agreements when free to do so, means that they are productive for the economy as a whole by definition.
How is this productive for the economy as a whole. This was done to keep salaries low, so a handful of people could make more money. How does that benefit the economy as a whole?
By allowing those firms to make more money. They are the economy too. The economy does not exist for one persons or class of persons benefit.
> This was done to keep salaries low, so a handful of people could make more money.
People cooperated to reduce their expenses without restricting the right of anyone else to cooperate. Just because people make money doesn't make it wrong. Conversely, a handful of people (the defendants) colluded to make more money by keeping salaries high, except they did it by restricting the rights of everyone else.
You seem to think that the "economy" in its (mostly or completely) unregulated form is some kind of ideal. Why? Such an economy is dependent on rational actors and perfect information, neither of which are present in human society.
It seems more reasonable that each human in a group will try to maximize their own economic outcomes as well as to assist the other humans that they personally care about in maximizing their economic outcomes. In the modern world, it's often expected that humans are able to extrapolate that the people that they don't know are similarly worthwhile human beings. So while it's generally considered acceptable to try to maximize things for themselves, doing so while knowingly making other humans worse off is seen as morally detestable.
It's important to remember that humans generally care much less about abstract ideals than they do about themselves, the people they care about, and their social standing. The "economy" as it exists in reality does in fact exist for the benefit of one class of persons: those persons who are willing to tolerate it and have the power to change it. When this real-life economy is no longer tolerated, it is changed, in ways like antitrust legislation, class action lawsuits against companies that participate in wage collusion schemes, and the French Revolution.
It wasn't demonstrated, it was assumed. Mostly because you will need broad understanding of economics. I'll try to do my best to demonstrate it. Imagine a smaller economy where there is only 1 firm. They have complete power to set wages, you don't like it you don't work. (We've already established this would happen eventually if agreements like this were allowed because it is far easier to control wages than it is to create new and competing firms.) What happens when they decide not to pay a living wage? More importantly, what is to stop them from influencing laws such that what becomes fair practice is changed over time? Is it fair to allow a single entity the power over not just the economy but the power to define what is just? We have to be very careful in a capitalist society about confining the limits of what actors are allowed to do because quite literally money often equates to power and with time power defines law. I hope it goes without saying that enough bad laws over a long enough time span are trouble for everyone in society. Unregulated capitalism will always lead to issues for a society because it always concentrates wealth. (Those with the most information and the best decisions always come out more ahead than the rest.) Remember, capitalism isn't the best way to run an economy its just the least bad.
Also, please remember you can't look at a statement in a vacuum. "Why isn't it? Those agreements don't restrict or infringe on the freedom of others to form different agreements, or avoid forming them." Perhaps not technically, but realistically they absolutely do. If we had a million worlds with a trillion firms and easy travel between them then such actions would automatically correct, but we don't and thus people do not realistically have the option to turn them down. The whole point of capitalism is to reward and penalize decisions. It kind of breaks down (predictably) when one side has enough power to prevent the downside of a bad decision.
Remember, free speech doesn't mean you can run into a theater and yell fire.