Market anarchists generally reject all forms of paternalism which deny the ability of free people to make reasonable decisions about their own lives. If someone wishes to trade their labor for a price they find acceptable, we wouldn’t use force to prevent it.
However, market forces naturally undermine exploitation. Market anarchists tend to see economic domination of working people as the product of statism and not the market. In a free society without Benjamin Tucker’s Four Monopolies over land, currency, patents and tariffs, the economic dependency proletarians have upon capitalists is virtually destroyed. Capitalism, in the sense of an unjust status quo characterized by state-driven monopolization of capital, depends upon a captive labor force whose better options are destroyed or precluded by state intervention in the market on behalf of a parasitic elite.
When people can work for themselves or in a horizontally organized workplace, they generally prefer it. Wouldn’t all of us prefer colleagues over bosses? In order for a capitalist firm to exist in a free society it would typically need to offer a much better deal to its workers, who would otherwise flock to better opportunities elsewhere — opportunities that are currently strangled in the cradle by the state.
So while market anarchists typically do not have an a priori moral opposition to wage labor, we have strong moral objections to the currently existing statist monopoly capitalism which makes wage labor a nearly inescapable trap.
In other words, opposition to the wage system in the sense of an unjust system of oppression doesn’t mean that some sort of anarcho-cops have to arrest people that voluntarily agree to work for or hire somebody else. By abolishing the state, we abolish state-driven monopolization of capital so that there would no longer be a “wage system” in which one’s only choices are working for somebody else or starving.