Originally, it was to give the middle finger to the government and to make their own lives without being taxed or controlled. Human and drug trafficking has happened over time, slavery too, but if you look at other countries, we don't look so bad, even to this day. However, that's not what this country was built upon.
Sounds like your history course is teaching what's convenient for their agenda because hating America is what's popular nowadays. I guarantee you they wouldn't enjoy living anywhere else. You might want to start learning some stuff on your own as well so we DON'T end up with the same problems as other countries, especially if your school starts praising socialism or calling one party good and the other bad.