Despite its noble sounding name this deliberately misnamed Act subverts workers' free choice about whether to unionize or not. Instead of voting by secret ballot, this Act also requires unions to be formed and recognized if half or more of the workers in an establishment sign pledge cards in support of this. So say, Tony Soprano style thugs knock on workers doors, stare across the dining table and hold the pledge card for workers to sign. Those who refuse can be intimidated, and everyone knows who is unwilling, leaving them open to retaliation down the line, or ostracism by fellow workers, or other unpleasant consequences.
So how do Krugman & Co. favor this over a free and fair vote by secret ballot? They essentially say that the means however imperfect justify the end, which is more unionization. This in turn will improve the lot of workers by extacting concessions from employers, and better redistribute wealth, thus narrowing the gap between the classes. If such ends justify the means, how about allowing the poor to extort money from the rich, or burglarize their homes to achieve redistribution?
Thankfully, it looks like card-check won't be able to clear the Senate with a filibuster-proof majority. Though many people take it as a given, I question the value of unions in many situations, or at least the premise that the pros outweigh the cons.
Unions to me are the most needed when through collective bargaining they are a counterweight to (mostly tacit) collusion by employers to keep wages and benefits below what would prevail in a free market. One example is of US hospital chains that were hit with a lawsuit over colluding to keep nurses' salaries artificially low, despite a national shortage of nurses. Another is of players' unions in professional sports (even though players may be super-rich.) They bargain with a handful of sports team owners that collectively decide on salary caps or player pay structure. But such employer collusion is relatively rare, and generally illegal.
Other pluses of unions include workplace safety, health and social benefits that they can win from employers through collective bargaining and the threat of strikes. I'm certainly for such health and safety measures, but for most of them they are better realized through passage of broader laws applying to all, instead of individually won through unions with the most leverage for their limited set of workers. Thus we have OSHA, or the Workmen's Compensation Act, and even the Minimum Wage Act and can go further along this route.