I agree with NeyF, "martial artists don´t fight", with this wording it may or may not express that they will use their skills, for instance, only at the fighting gym.
The same goes to your sentences Vitor, they would be understood (on some given contexts).
One other way that could be accurate (but then again, it depends on the context) would be: "martial artists, doesn´t just go out there to pick fights.", with emphasis on the fact that they don´t get around purposely/intentionally to start fights.
Thus, they might use their skills only in case they are in a tournament or if they attacked first and have to guarantee their own physical integrity or that of others. So they may use, though sometimes unwillingly.