Perry wrote the linked article taking the Major League Baseball Players Associations to task for not acting like a "genuine trade union" and not supporting the umpires when they went on strike or organizing the minor leaguers.
First of all, the MLBPA is not a trade union. It's a company union. It's an entirely different animal. A trade union, such as the United Auto Workers, tries to get the best deal for all types of people doing various jobs in an industry. A company union, like the MLBPA, can only represent people who are employed by one entity, Major League Baseball. And all of those people have one job: they play baseball. This also means that MLBPA can't organize minor leaguers either. They're in the wrong company. If this were something like "The International Association of Baseball Players" then you might have a case. But it isn't.
Second of all, Perry tosses this line out "Genuine labor unions -- the ones fighting for the living wages and workplace safety of plumbers and stevedores-are fellow travelers with other unions, often marching in one another's picket lines."
Hmm, I'm a union member. I know I've crossed picket lines. I've known a lot of other members of my union who have crossed picket lines. Some people care about such matters. Others don't. We seem to get by OK.
Perry seems to think that labor unions are only groups of blue collar workers who work against gritty backdrops like in "On the Waterfront". But there are a lot of white collar unions. And there are still company unions, like MLBPA. And their aims are entirely different from what the AFL-CIO, SEIU or the Teamsters have.