If you report to a manager chances are good you have developed pre-emptive, almost reflexive reactions to the sound of their voice. When they call your name, your heart rate increases a little, your eyes open wider, you sit straight and respond with an attentive "Yes?" You're anticipating one of two things:
#1: An order/instruction
#2: A query/reprimand
Very, very seldom do they call you to make idle chatter or to praise you. (Consider yourself the exception if you receive praise from your manager more than once a month.) A manager cannot be too nice because they risk making the manager-staff relationship casual. Staff become more relaxed and managers fear relaxed staff because in a typical company the mentality of management is that staff must be kept on their toes if they are to perform. Therefore experience causes you to develop an unfavourable reaction to your manager when they call your name, because experience tells you it's going to relate to one of the above two things. You don't expect anything good when you hear your name called to you. (It's perfectly natural, don't worry.)
Having a manager sucks, full stop. When they're making you work your behind off yet micro-manage you by asking for feedback on your progress every hour, it becomes very easy to hate them. You think to yourself that you would never be like that if you become a manager. You need to look beyond your relationship with them and see their other responsibilities though. They report to a senior manager: you don't. The senior manager does not reprimand or question you when you make an error or don't perform your duties; the senior manager gives your manager the flack. For all intents and purposes your manager is the one responsible for your work. In management meetings behind closed doors a manager is the face of her team, and she is accountable for the performance (or lack thereof) of that team. If her team isn't on top of everything, she's viewed as a poor manager - no further explanation or excuses are needed. If your manager is embarrassed or construed to be a non-swimmer among senior management, the whip is going to be cracked and you along with your peers will need to work even harder to make things right. Accountability travels upward, flack travels downward.
Even the senior manager reports to a general manager; the general manager to the vice president; the vice president to the senior vice president; and finally the senior vice president to the CEO. In this hierarchy, it's almost always the person immediately below that gets the scolding when something goes wrong. Knowing the reason for something doesn't matter; the person responsible is all you need to know. The scolding travels all the way down and stops at the employee that has to actually get out and fix the issue at hand. Through this all though, remember that very few people actually take pleasure out of being douchebags, it's just that their job often forces them to. Managers have to manage people, and often it isn't fun.