If it is your belief that the natural state would be no right-to-work laws and no anti right-to-work laws then I would agree. But given the sordid history of unions in the US - especially over the last forty years or so - I prefer legislation that protects an individuals right to work unfettered and unmolested by monsters.
The fundamental problem is that the fe'ral government has decreed that if 51% of the current employees of a plant want to form a union, they can force their will not only on the other 49% of current workers, but also on the countless people who might decide to work there in future. While I agree that the proper remedy would be to say that employers should have the freedom to either negotiate whatever sort of contract they want with unions, or refuse to deal with unions and fire anyone who refuses to work on the employer's terms, the fe'ral government won't allow that. Since fe'ral rules don't allow an employer to decide whether to accede to union demands, restricting the demands unions can make is probably the best protection states can offer.