The laws differentiating between a contractor/employee vary based on country, state, etc. But at the core they are the same thing. One party is providing compensation in exchange for a service.

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.

Good point about services that you don't want/need/like but is an employee really providing a service? Isn't some onus of responsibility on an employer as the One in the position of power? I think employing someone should be a long term commitment that involves education to bring them up to a level that you consider good enough. Otherwise shouldn't you just outsource the work?

Employers typically impose must more stringent requirements than a typical contract. For example, I can have multiple car mechanics, but typically can't work multiple jobs, and have multiple on back up if one falls through.