As stated above, students have different reasons for initially beginning Taekwondo training. Since Taekwondo training involves learning techniques designed to injure or kill a human being, you should want to know why you desire to learn such techniques.
You have a right to learn to defend yourself from the criminal element of society. However, if you feel the need to beat up anyone who offends you, then you have a problem. You need to examine the reasons why you think that beating someone up is going to solve your problems. Taekwondo instructors will not necessarily reject you as a student if you exhibit these aggressive tendencies, but they will watch you carefully and expect Taekwondo training to change these tendencies.
If you are ever in a situation where you must defend yourself, you have the right to use any reasonable force necessary to protect yourself, but you must still have compassion. No matter how angry you get, you must remember that every attacker has parents, family, or someone who loves and values them. Your actions will also affect their lives.
Violence for the sake of violence is a never-ending cycle. When you respond to violence with violence, the attacker will respond with more violence. You must use your creativity, dignity, integrity, and honor to end the cycle. You must use every way you can to avoid violence, but when it is inevitable, and then you must be the victor. The longer and harder you train in Taekwondo, the less need you will find for the physical aspects of the training. You will find yourself dealing with people on more of an intellectual and psychological level.