The mayors comment of slavery even as economic comparison is idiotic rhetoric.
In the right-to-work states that Sullivan likes, the unions have little influence to improve the plight of working people. By eliminating or reducing collective bargaining the end result is lower wages, benefits and insurance.
Right-to-work states offer lower wages to increase profits for the companies, which is enticement for people to relocate; compelling people to work for less.
While reducing union power or eliminating them does not make slaves of the employees, it certainly put the employers in the position of plantation owners.
They can hire and fire without cause and persuade themselves that their employees should be happy since they gave them a job to buy food to eat and a place to live. But not too much, because that would reduce profits or raise taxes.
The mayors comments sound more similar to those of Donald Sterling than someone representing the people, not just the rich contributing to his campaign.