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 , আপনি don't get to respect it when আপনি have it and আপনি do realize its importance once আপনি don't have it anymore. But yeah , still some stupid people dislike him. Haters gonna hate আপনি 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 আপনি look at him , turn a blind eye অথবা not. আপনি still can't deny his excellent music.
His সঙ্গীত 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 প্রদর্শনী michael jackson's bad was played and he even sang and danced to it although he hates him.

Like i ব্যক্ত michael is de king of pop but thy hate him