You cannot rely on the “Good Guys” to protect you from the “Bad Guys"
For one thing, the good guys are not always around and, if they are, you cannot be sure they will help. Also, you never know who they good guys are. Taekwondo will teach you how to defend yourself when the need arises; the one person you may count on. When you are in need, YOU are the only one that is always there, and that who is ready and willing to help no matter how great the danger.
You can do it
No matter who you are, there are things you may do to defend yourself effectively. Defense is usually always better than submission.
Nothing else matters
When you are facing an evil person intent on harming you, nothing else matters except your preventing the person from harming you. His bad childhood, the lack of school funding, liberal judges, corrupt police departments, your efforts in the peace movement, your being a good person, etc. mean nothing at that moment. Taekwondo teaches you what you need to do; whether you do it is up to you.