For good reason. They prevent accountability among police: http://reason.com/blog/2014/08/14/police-unions-produce-rule....
They also prevent educational innovation: https://www.amazon.com/Special-Interest-Teachers-Americas-Sc... and pr event urban schools from even functioning.
As the topic article points out, construction unions are attacking the housing supply.
Should it be a surprise that anyone who pays attention is unhappy with unions?