Almost everyone who has ever had a job has had the misfortune of working for a mean boss. Not all mean bosses are necessarily mean (some may simply appear that way either because they too are working for a mean boss or have poor interpersonal skills) but for many managers it is not uncommon to think that the only way you can get good work out of your subordinates is to treat them like *^%$.
Not treating your employees with respect and empathy can create enormous bitterness in the workplace and force good employees to quit. Or in the extreme cases, lead to violence in the workplace. Natavia Lowery, personal assistant to Linda Stein, former manager of the Ramones and realtor to the celebrities, has been charged with killing her boss for mistreating her. It is not something that happens every day but the point is that when you abuse your employees, they do harbor negative feelings towards you. If an employee is not performing, the best course of action is to suggest training, provide mentorship, and if it fails, just ask them to leave. (Related: How to make employees happy)