Union intimidation goes back decades almost to their beginning.
It goes to the beginning. If a union did not present a threat of violence and sabotage towards any company that dared to hire replacement workers, than a strike would just be a mass resignation.
The court acknowledged that using threats and force to obtain property is wrongful. However, the court reasoned that it is considered "wrongful" only when the perpetrator has no "legitimate claim" to it. Since federal law empowers unions with the right to strike, the use of violence to secure higher pay and benefits was not extortion. The case was dismissed. Such violent acts can, however, be punishable under normal state or federal laws.