Turns out it's a trademarked name, which they didn't know. Needless to say, the Belgian radio show will be changing it from "King of Pop" to something else. 

“It says that we are not allowed to use that name just like that. We did not even know that ‘King of Pop’ was a protected trademark,” [Van de Voorde] told Het Nieuwsblad. “It is pretty cool that these people know we exist, but it is kind of stupid that they are making such a fuss about it.”

Heirs of Michael Jackson demand that Belgian radio show ‘King of Pop’ changes name