The episode this is from was about Steven wanting justice for Sadie. This scene -the lesson- is never reflected upon within this episode nor given attention to in any future episodes, meaning this is not part of a Grand Arc Duvelopment.
The sentence in the episode was simply put there to make the action a bit questionable, with the same sentiment that Sadie WAS perhaps in the right.
They went through with it, Steven was hype, Lars became a fire-breathing lizard, hilarity ensues and the narrative does not want us to feel bad for Lars. He had it coming. It was ok.
Steven should know what it is like to defend your friends. To fight evil. To bring justice. But he is not like this anymore now. Now suddenly fighting for your friends (whatever is left of them??) is bad. Most likely because a big angry black woman is thinking this. Steven did no effort to understand Bismuth. They antagonize those who are hurt for wanting to defend themselves. This comparison here is that the show lost it touch by losing its heart.