I suppose there are times when that's true. For instance, limiting the work-week to 40 hours, and after that time-and-a-half. You may prefer a 50 hour week or a 30 hour week.
It can be way more fundamental than that. Sometimes it can be even be an ethical disagreement over some issue.
But, long story short, I view that loss of freedom as similar to the loss of freedom living in a society. You miss out on some autonomy, but in return you get a range of benefits that should more than compensate you. And a voice (via elections) in what those benefits are. While occasionally you'll be screwed some, it's hard to imagine how a system could work that didn't do that to anyone, ever.
I'm fairly pragmatic about that, and I agree with you that sometimes you trade some fundamental rights by living in a society. But the system of that society is pretty important. The United States is currently polling as 70% Christian. If we straight off voted via an election to make that the official religion of the country and started enforcing certain beliefs over the remaining 30%, that would be a bad system of government. Instead we have a system that says that no matter what the majority of people believe in, individually everybody has the right to believe or not believe in whatever they wish, and that right is not to be infringed upon. Protecting individual freedoms from a tyranny of the majority is something I believe in.
It may be "unfair", but it is definitely the results of a free negotiation between two parties. Now, if you want to discuss limiting their freedom to enter into contracts with each other, that's fine. I don't think that freedom is absolute. But as most people professing your beliefs are fairly libertarian in outlook, I'd like to impose on you to explain why it's okay in this case. Especially since the right you think it is imposing on is your right to enter into a contract with one of those parties under your preferred conditions.
You've sort of got me pegged, but libertarians come in a spectrum. Sometimes when you just see the most vocal among us, you can get the wrong idea. For example, I'm a libertarian who is very much in favor of strong anti-trust laws. I come to this belief because even though I believe the free market is the way to achieve the best results, I also believe monopolies are a failure mode. In fact, the general distrust of the ability of government to take on duties that I believe are best handled by private enterprise is because the government is a monopoly, so having any one company be the monopoly isn't any better. In this case, I see the union as the monopoly, if you're not allowed to work without being a member.
I believe the original intent was to try to damage unions by allowing free riders, and also make it harder to have a de facto union shop.
I agree, and like I said, I'm against such laws.