Kids learn right from wrong because you model it for them. You don’t trash rooms. You don’t break things. You tidy things up. They see that. They already know it. They know that the room trashing is wrong, that is why they did it in the first place. Because they had so much anger and frustration they desperately wanted you to listen and to acknowledge. So they did the worst things that could think of to do in the space that they were in. Was the child isolated at that point? If a child is desperate for you to hear them and to understand the depths of what they are feeling and just how angry they are, and you send them away from you, and do not give them an outlet for those feelings, this seems a fairly logical next step for them. A physical example of how bad they felt and a way to punish you for taking them away from others and isolating them when they needed guidance the most.
The way the child sees it, you started it - we might not agree with this of course by doing tit for tat punishments we really are stooping to the level of seven year olds. “If you don’t give me that toy I’ll tell” “if you don’t put that away I’ll take it away from you”. How can they differentiate between these things? How can the child respect you if you are acting like their friend at primary school?
Where did the “must follow through on threats” thing come from? Why threaten things in the first place? Why do we threaten children? Why not show them that their behaviour makes you angry and frustrated but that you can and will calm down and be able to sort things out rationally - that is what you’d like them to do, is it not? You are sticking to what you said in anger and refusing to back down, they are sticking to what they did in anger and refusing to tidy it, you are not giving them skills by doing this.
Don’t isolate children when they are angry, they need you because they don’t have the level of control needed.
Don’t punish a child for letting their anger out in the only way they knew how - you are teaching them to suppress their feelings and to turn that anger inward on themselves next time. Give them ways and outlets for anger - you wouldn’t tell them to shut up and stop crying and tell them they are not allowed to be sad and if they are you will send them away, would you? Same with anger. It’s a normal human emotion and you cannot stamp it out of them by force.
Think of how you would feel if your room was in the mess theirs is? Even if they are braving it out, they are upset about it. They are upset too by their power to destroy things. They are worried about what is going to happen.
Punish them if you like, go for it, take everything away, but that is clearing up their mess, is it not?
Have you asked the child what they think should happen now?
I would be leaving the room as it was for a while. It’s their room. And it will let them have some control back. They lost control big time and they are probably embarrassed. Believe that most children do actually want to be good people. Leave some time and see what happens, and give them better ways to let their anger out next time - not by repressing it or destroying things.
Anyone is free to say none of this makes sense and I should send all their toys to the charity shop. I’m not saying that’s the wrong way. I am saying though that children are people, and normal, and learning, and they are learning from you.