why do they still play on the radio when they hate him

They no longer hate on him after his death.
It's just like every valuable thing , あなた don't get to respect it when あなた have it and あなた do realize its importance once あなた don't have it anymore. But yeah , still some stupid people dislike him. Haters gonna hate あなた know. No matter what.
Even when he was alive , still his songs were being played on Radio I believe like "Heal The World" , "Billie Jean" etc. No matter how あなた look at him , turn a blind eye または not. あなた still can't deny his excellent music.
His 音楽 had great messages in it.
:D

Some people hate him and enjoy his music. One of my classmates hate him and talk bad about him but during our school's talent 表示する michael jackson's bad was played and he even sang and danced to it although he hates him.

Like i 発言しました michael is de king of pop but thy hate him