"Violence is the last refuge of the incompetent."
-- Salvor Hardin; Isaac Asimov, Foundation (Foundation Novels)
is total garbage. It is one of the first means used by the incompetent; it is the last refuge of the competent. Competent people tend to try (or at least consider) almost everything else first.
"Asimov maintains the theme throughout the entire series, always showing how creativity and reason can overcome the simple strategy of the bigger gun every time." Adam Hobson
At least it can if you're writing fiction for academic twits. Even as a teenager I thought the Foundation trilogy was pretty shallow.
The real world doesn't care about a person's beliefs, just because you want to be able to solve a problem without violence is no evidence at all that such a solution is possible, much less the best way out. Sometimes violence is necessary.
"Anyone who clings to the historically untrue - and thoroughly immoral - doctrine that 'violence never settles anything' I would advise to conjure up the ghosts of Napoleon Bonaparte and the Duke of Wellington and let them debate it. The ghost of Hitler could referee, and the jury might well be the Dodo, the Great Auk, and the Passenger Pigeon. Violence, naked force, has settled more issues in history than any other factor, and the contrary opinion is wishful thinking at its worst."
Robert A Heinlein, Starship Troopers
I think everyone should read this novel for its fairly thorough discussion of military morality and the ethics of violence. Not just everyone who might use violence, but also everyone who may be affected by organized violence, that is, by military action. Professional philosophers will pick lots of nits about Heinlein's claims and illustrations, I don't agree with all of it myself, but it may get some people thinking, including many who will likely never read any nonfiction.
Everything has unintended, and often unpredictable, consequences. The side-effects of violence are almost never good. Especially if you make the mistake of using it against a Flinter, or one who believes with them:
"Never initiate force against another. This should be the underlying principle of your life. But should someone do violence to you, retaliate without hesitation, without reservation, without quarter, until you are sure that he will never wish to harm - or never be capable of harming - you or yours again."
-- from THE SECOND BOOK OF KYHFO (Revised Eastern Sect Edition)
-- F Paul Wilson, Lanague Chronicles
No one sane would use violence against someone who believed like that. The risks would simply be worth more than they could possibly gain. You might also like to check out F Paul Wilson's contemporary fantasy series about Repairman Jack, the first and one of the best of them was The Tomb (Adversary Cycle/Repairman Jack). Even in those people with less extreme beliefs, it can lead to feuding or to people avoiding dealing with the violent person.
There is a supposed "old Chinese saying": The wise man defends himself by never being attacked. Which is excellent, if incomplete, advice. I completed it myself with "But only an idiot counts on not being attacked." Don't use violence unless you really need to, but if you need to don't hold back. Nothing else matters much if you don't survive.