"If you're sizable, half the men ye meet will fear ye, and the other half will want to try ye. Knock one down […] and the rest will let ye be. But learn to do it fast and clean, or you'll be fightin' all your life." (11.176)
Sometimes violence is the only answer to a problem, at least according to this advice from Jamie's dad. However, it's important to note that while he encourages his son to fight, he also encourages him to get it over with as soon as possible. Violence should only be used sparingly, and as a last resort.