I’ve heard this question a few times, and yet it still surprises me at times. Unfortunately most of what people know about Jiu-Jitsu comes from movies and professional fights, which are about entertainment and not really an accurate representation of the art.
Jiu-Jitsu is a grappling based art, not a striking based art, in which the goal is to use superior technique, leverage and strategy to control (not hit) an aggressive opponent.
One of the fundamental assumptions in Jiu-Jitsu is that for a technique to be considered “good” it must be functional against a bigger, stronger, more aggressive opponent.
With that idea in mind, that your opponent will be bigger and stronger than you, it is impossible to rely on the idea of overpowering them with strikes.
Jiu-Jitsu is the “paper” of rock-paper-scissors. It is not about trying to have a bigger rock, it’s about getting a hold of that rock and making its size as irrelevant as possible through technique and use of leverage.
Jiu-Jitsu is not about violence, it is about learning how to control violence. To slow it down, manage it and redirect it. In Jiu-Jitsu acting overly aggressive tends to get you in more trouble then anything, where a slower, more methodical practitioner can easily take advantage of that aggression.
Jiu-Jitsu will not make a child aggressive, but it can teach them to control aggression in others as well as them-self.