When Sony hired commercial moving company Sher-Del Transfer to relocate its U.S. headquarters from midtown to the Flatiron district, it unwittingly triggered a political and labor backlash.

Brooklyn-based Sher-Del is a member of the Metropolitan Movers Association, a trade group consisting of moving companies and two unions representing their workers. It “was founded to protect free market values,” its website says—that is, an environment in which movers can compete for jobs without the government creating an uneven playing field.

But Teamsters Local 814 considers the Movers Association’s unions to be shams aligned with lower-paying companies. Of the trade group’s two unions, Local 514 of the Brotherhood of Amalgamated Trades appears to be the union’s only local, while Local 1212 of the United Service Workers Union claims to include 20 locals nationwide.

But companies in the Movers Association—which bid against each other for jobs as well as against Teamsters-affiliated movers—say their workers receive good pay and benefits. They are livid that the Teamsters use terms like “bottom feeders” to describe them.