There can be many reasons why a manager/supervisor bullies one or more of the employees. But whatever the reasons may be, it always points to the ineffectiveness of the person in the role of a manager or a supervisor. This person simply should not be in a managerial position.
All good managers and supervisors realize that each employee is an individual and likely has his or her own characteristics and personalities. It is likely that what works as a successful motivational approach for one employee may not be the right approach for other employees. It is possible that some employees are used to being subjected to yelling and shouting, and they might get motivated when the manager uses that kind of motivational technique. However, for most employees yelling and shouting do not work. Most employees look at this as verbal abuse and as a demotivating factor. Work becomes extremely stressful for them and it starts affecting their personal lives.
A good manager is able to figure out what approach works best as a motivating factor for each and every employee and uses an individualized approach, instead of one approach for all. Quite often a reasonable sensitive but firm approach works for most employees. All employees know that they are there to do the work and they get paid for doing their jobs well. If someone cannot perform his or her job function, then there are other ways to manage their performance, but yelling and shouting is never an answer.