The word "bu" of budo (martial arts) is written with the Chinese character for "stop" within a character signifying two crossed halberds meaning to stop conflict. Since karate is a budo, this meaning should be deeply considered, and the fists should not be used heedlessly.
Youth is justice and vigor. Vigor is stimulated by bu (martial arts) and it overflows into good or sometimes bad actions. Thus if Karate-do is followed correctly, it will polish the character, and one will uphold justice, but if used for evil purposes, it will corrupt society and be contrary to humanity.
Master Gichin Funakoshi
From The Karate-do Kyohan
use stillness to overcome movement