I try my best not to encourage senseless behavior.
Listening to our thoughts before we say them helps us be kinder.
It's not hard, try it.
There are two major causes of discord:

Senseless Behavior, Level One:
This is the impulsive brain of someone who is immature and unwise. It's fine to experiment, but this action can range for a loud sound in the classroom to putting others in danger, and yourself by doing something that is not thought out and results in destruction bringing discord.
Interacting in this situation, we pause, breathe and go for it.
Explain halting.
Explain the object to not touch and why, say "Sharp _____." "Dangerous _____."
Explain what we must do  to be careful and play and learn for the self and others.
Gentle mind, gentle results.

Violent Behavior, Level Two:
Actions done through senseless thoughts causing violent behavior. Think of one done through the former.
Interacting in this situation we pause and watch for a sign of pain or the person hit saying a message, and the other apologizing. If all of these are not met, we breathe, step in.
"Listen to me."
"We are all friends here, and we do not hurt our friends with our hands."
"We keep out hands on our own bodies when we feel angry."
"When we touch we do so kindly."
"We use gentle hands, gentle words. What gentle words do we say now to each other?"
"Was there a message one of us wanted to say?"

"Everyone has a vital role in this team. We protect. Our hands are gentle, our words are gentle."

"It's okay to feel anger, but it's better to walk away, and keep our hands off our friends and our words out of their ears."