Final answer:
Workers and managers at the Van Nuys plant likely objected to just-in-time inventory and the dehumanizing aspects of Taylorism, which affected job security, wages, and workplace conditions.
Step-by-step explanation:
The workers and managers at the Van Nuys plant objected to various aspects of the Toyota production system, but based on the information provided, the focus of their objections was not explicitly on any of the given choices like lean manufacturing principles, worker empowerment, or quality control methods. Instead, their objections likely revolved around the just-in-time inventory system. This system, which reduces warehousing jobs and puts downward pressure on wages and benefits, could have been seen as undermining the job security and bargaining power of union workers. Additionally, the Taylorism approach or scientific management, which dehumanized workers by timing their movements and rationalizing production processes, was also a probable target of worker and manager dissatisfaction due to its impact on the nature of their work and workplace environment.