I don't have a problem with people being forced to pay dues regardless of their union membership, as even the non-member workers benefit regardless of their individual participation. If people want to not pay dues, then I'm fine (well, not literally fine, but anyway) with their employer being able to ignore labor laws regarding the non-paying members; no more 40-hour work weeks, sick days, raises, etc for the non-payers. If they don't want to pay for the benefit, they shouldn't get the benefit.
Right-to-Work laws really ought to be re-named "Right to Get Treated Like Shit and Fired for Whatever Reason We Wish LOL" laws, because that's all they are. Letting people "opt out" of paying for the benefits they use just means no one will pay, and the benefits they like will just go away without anyone left to fight for them. Which is, y'know, the point.