Although none of us are enamored with North Korea, there was a fair share of atrocities that were committed by UN forces on the NK population and the South Korean government against communist sympathizers in their own country. The Wiki article goes into it in some detail. (No, it doesn't make it OK because "they were doing it".)

(As an aside, I sometimes bitterly contemplate how many great Korean minds were lost in that war because of their personal politics)