What if we replaced "employee" with mechanic? Would you be in favour of making it illegal for people to switch mechanics 'at-will'. Then you would have to prove that your mechanic was terrible before you could use someone else.
People that oppose 'right to work' and 'at-will' employment tend to not understand this until you put them in the position of the party that is providing the compensation. Once they are forced to pay for a service they do not want/need/like they are less likely to support laws like the ones in the article.