Some people mistake outbursts for strength. The loud, emotional display of "strength"—when they're upset, hurt, angry. When they curse. When they throw insults. When they try to put other people beneath them. When they blame everything else but themselves.
This behavior is sometimes considered part of a "strong personality."
They think that by arguing and not backing down, they're the stronger party. And they think staying silent is weakness, even when it's the smarter choice in some (if not most) cases.
Outbursts are symptoms of weakness. It shows lack of self-control. Lack of discipline. It's the mouth throwing regrettable words faster than they can control their temper, faster than they can think and be calm. It shows their being ruled by emotions.
Empathy, kindness, understanding, patience—these are much harder to give, and require much more strength. It shows mastery of self.
Strength is found in quiet conviction, not in a loud, bloated ego.