FWIW, when I worked at Hechinger in Maryland in high school and college summers, I found a manager's anti-union toolkit. It was a detailed booklet describing how a manager should address calls for a union, deal with the media, and report to headquarters about organizing. Hechinger drug tested employees (it's really fun to pee in front of another person) and did personality tests. I was a very hard working employee at Hechinger, and didn't think that the company needed to be organized. But finding that booklet was a real wake up call. The tactics seemed unfair; they were designed to squash the debate instead of having some form of democratic choice or dialogue. In retrospect, I realize that Hechinger was taking advantage of me and other employees. They kept me on part-time status, despite my weekly hours that often hit overtime. That not only stopped me from having benefits, it also displaced the normal full times who did get benefits. I worked really hard there for no good reason. Hechinger went bankrupt when faced with competition from Home Depot and Lowe's. Anyway, back to Wal-Mart:

...While its [Wal-Mart's] workforce has one of the best productivity records of any US corporation, it has kept the compensation of its rank-and-file workers at or barely above the poverty line. As of last spring, the average pay of a sales clerk at Wal-Mart was $8.50 an hour, or about $14,000 a year, $1,000 below the government's definition of the poverty level for a family of three.[4] Despite the implied claims of Wal-Mart's current TV advertising campaign, fewer than half— between 41 and 46 percent—of Wal-Mart employees can afford even the least-expensive health care benefits offered by the company. To keep the growth of productivity and real wages far apart, Wal-Mart has reached back beyond the New Deal to the harsh, abrasive capitalism of the 1920s...

One of the most telling of all the criticisms of Wal-Mart is to be found in a February 2004 report by the Democratic Staff of the House Education and Workforce Committee. In analyzing Wal-Mart's success in holding employee compensation at low levels, the report assesses the costs to US taxpayers of employees who are so badly paid that they qualify for government assistance even under the less than generous rules of the federal welfare system. For a two-hundred-employee Wal-Mart store, the government is spending $108,000 a year for children's health care; $125,000 a year in tax credits and deductions for low-income families; and $42,000 a year in housing assistance. The report estimates that a two-hundred-employee Wal-Mart store costs federal taxpayers $420,000 a year, or about $2,103 per Wal-Mart employee. That translates into a total annual welfare bill of $2.5 billion for Wal-Mart's 1.2 million US employees.

...Every store manager at Wal-Mart is issued a "Manager's Toolbox to Remaining Union Free," which warns managers to be on the lookout for signs of union activity, such as "frequent meetings at associates' homes" or "associates who are never seen together...talking or associating with each other."

The "Toolbox" provides managers with a special hotline so that they can get in touch with Wal-Mart's Bentonville headquarters the moment they think employees may be planning to organize a union. A high-powered union-busting team will then be dispatched by corporate jet to the offending store, to be followed by days of compulsory anti-union meetings for all employees. In the only known case of union success at Wal-Mart, in 2000 workers at the meat-cutting department of a Texas Wal-Mart somehow managed to circumvent this corporate FBI, and voted to join the UFCW in an election certified by the National Labor Relations Board. A week later Wal-Mart closed down the meat-cutting department and fired the offending employees, both illegal acts under the National Labor Relations Act. The NLRB ordered Wal-Mart to reopen the department, reemploy the fired workers, and bargain with the union, but Wal-Mart has appealed the NLRB decision and the litigation continues.