There is no room for bullying and harassment in a workplace. Employees perform best in a positive and rewarding environment.
Most employees in the United States want to do a good job. They like to feel like they are contributing and earning the salaries they are receiving. That is why it really should not take a lot of work by the supervisors and managers to keep them motivated. However, the environment at work can have a significant impact on the performance of the employees.
Most employees like to see a work environment that is positive and rewarding. On the other hand, if they are constantly being bullied and harassed by their supervisors and managers, it is bound to impact their performance negatively.
It is true that it is the job of supervisors and managers to make sure everyone is performing well and is either meeting or exceeding their expectations. However, if someone is not performing, then yelling and shouting is not the answer. In cases like that, the supervisor/manager needs to work with those specific employees and go through a performance management process, which may include performance improvement plans including possible training and at times change of assignment. But it is never necessary to yell and/or shout at employees even if their performance is not satisfactory.
Some supervisors and managers believe that even for employees who are doing well, it is important to yell and shout to keep them motivated. But that is absolutely the wrong thing to do. Most employees will only become demotivated if there is bullying and harassment at work.