This might be the most common argument you hear against Right to Work, perhaps second only to "Right to Work for Less" which is also bunk. But this is the argument with teeth and was considered above debate; "it's not fair that we have to represent workers who don't pay dues." Well, it appears they don't have to. This being the case, Right to Work couldn't be more fair.
Those who want union representation get it and pay for it; those who don't want it don't get it and don't pay for it. This is the REAL pro-choice position.