Arguments like this are fine in the world of ideas, but miss the reality people live with every day.
Sure, in theory, an individual is free refuse a job offer and go look somewhere else. In practice, though, most people are dealing with very real externalities that severely limit the wide range of options that are available in theory.
Someone trained in a specific skillset, providing for a family, and tied to a particular city or town (as most of us are) typically has only a handful of employment options where he may apply his skills and earn a decent living to provide for his needs and the needs of his dependents. When all of the available employers offer unjust or exploitative terms of employment, the individual is effectively coerced into allowing himself to be exploited; no force or threat of violence is needed.
This is why anarcho-capitalism will never work. Without a societal structure people can trust to mete out justice and look towards the common good, to whom would the individual have recourse when he is wronged?
