I'm not sure if you're referring to US history, but the "protection" that unions got only came later. The original unions only had the threat to walk off as "protection".
I said that. In those cases, I don't object to unions much or at all. However, that's not the status quo today, contrary to what you implied. Unions today are protected by the government far beyond what free trade would give them.
Why should corporations exist with "legal protection" if unions should not? What do you think patents are? What do you think copyrights are? What do you think contract law is all about? You live in some Cato Foundation fantasy world where you honestly believe you could survive for 2 days without "legal protection". You probably also believe that your "success" and "wealth" exist only due to your hard work and talent and the government only holds you back, right?
I'm not a laissez-faire capitalist, nor a libertarian. I'm in favor of government regulation to help the poor and achieve other social goals. I also agree that unions were important historically in improving the standard of living in America, if only because of the lack of other options. However, I don't think most unions are good for society at large today, and I think government protection of unions should end.
I'm not about to get into an argument about why I think all this, particularly not on Slashdot. I only posted to object to your implication that collective bargaining as we know it today is the result of a free market. It's the regulations prohibiting the employer from firing union members that require them to negotiate. Otherwise most unions would be destroyed pretty quickly.
What you want is a return to the days when all the power is in the hands of the employers. It sounds like you're some free-market religious fanatic or something, and I'm not sure why I even took the time to respond. When you can find a single case in human history when a "free market" existed and made anything better for anyone, then you can be taken seriously.
You were the one who first mentioned free markets, not me. You were trying to paint today's teachers' unions as the product of a free market (or at least that's how I read "Should they not be allowed to negotiate their best pay package? Don't you trust free markets?" in your post). I never said I supported totally free markets, and I don't.