Final answer:
It is true that after World War I, employers opposed unions by supporting the open-shop movement. This movement was part of the American Plan, which aimed to undermine unions by advocating for the appearance of freedom while employing tactics to weaken collective bargaining.
Step-by-step explanation:
It is true that employers actively opposed unions after World War I by supporting the open-shop movement. Post World War I, business owners and industrialists leveraged the anti-union sentiment prevalent among the public to counteract unionization through open shops, which were part of the broader American Plan.
This plan promoted the idea that open shops were synonymous with American values like freedom, despite criticism that it was a guise for antiunion activities that undermined worker rights. Additionally, employers used tactics such as hiring strikebreakers and yellow-dog contracts, all designed to weaken the collective bargaining power of unions.
During the 1920s, businesses lobbied to outlaw collective bargaining, arguing that individual workers should have the freedom to contract independently. This argument was seen by labor leaders as a pretext to reduce union power. The Taft-Hartley Act of 1947 further challenged union growth by allowing workers to opt out of unions, leading to a decline in union membership levels post-World War II.