The uncle wasn't senselessly blaming Seunghyeon. He clearly perceived the reaction Chaejun had when he asked him about the taekwondo kid to be negative and seeing as Seunghyeon was crying and all that's a logical train of thought. That night he was discussing it over the phone too about how to handle the situation.
And since it seems like it was the uncle that got hurt, he wasn't at the scene to see Chaejun's situation and likely assumed he was locked in as a nasty kid's prank considering he already had suspicions. The workers who found him probably didn't go past mentioning they found him unconscious in a storage room.
The uncle wasn't senselessly blaming Seunghyeon. He clearly perceived the reaction Chaejun had when he asked him about the taekwondo kid to be negative and seeing as Seunghyeon was crying and all that's a logical train of thought. That night he was discussing it over the phone too about how to handle the situation.
And since it seems like it was the uncle that got hurt, he wasn't at the scene to see Chaejun's situation and likely assumed he was locked in as a nasty kid's prank considering he already had suspicions. The workers who found him probably didn't go past mentioning they found him unconscious in a storage room.