Some defense mechanisms are:
Projection. This involves unconsciously projecting your own unacceptable feelings onto other people; you do not have to own them. For example, some fear that people who learn the martial arts may lose their temper in an argument and physically attack someone. They think that since they might lose control of their own anger that others might do the same. Projection is a particularly insidious defense mechanism, because it not only prevents a person from dealing with his or her own feelings, it also creates an attitude where he or she thinks everyone else is directing his or her own hostile feelings back at him or herself.
All people have violent, and even homicidal, impulses. For example, it is common to hear people say "I am so mad I could to kill!" They do not mean it; they are simply acknowledging their anger and frustration. Most people acknowledge feelings of rage, fear, frustration, jealousy, etc. without acting on them in inappropriate or destructive ways. However, some people are unable consciously to admit that they have such emotions. They may believe that "good people" never have such feelings, when in fact all people have them. Many times, these people have higher than average levels of emotions and fear that if they acknowledge their hostile feelings; they may lose control and really will hurt someone.