Justified would mean legal in the eyes of the law, necessary would mean required to save life and limb, ok would mean you're happy with the way things worked out. I could see where I might be justified in using violence, and it might be necessary, but I wouldn't be ok with it(or at least the circustances that led to it, if I could somehow have avoided the necessity).
Light a fire for a man, and he'll be warm for a day, light a man on fire, and he'll be warm for the rest of his life...
Discussion is an exchange of intelligence. Argument is an exchange of
ignorance. Ever found a liberal that you can have a discussion with?