After receiving criticism from listeners who said it wasn't fair to base the decision on the political leanings of his father, National party leader and Prime Minister John Key, RDU posted a follow-up comment saying their decision was based "purely on the song".
"We have the upmost respect for real musicians and artists. However, having suffered through listening to this song we can guarantee this does not meet the RDU standard."
The move comes after Key hosted his first radio show on Tuesday night, playing his debut single near the end of his hour-long effort on George FM.
Rumoured to be about his ex-girlfriend Amelia Finlayson, Forget You is reported to be a house-influenced "banger". The song isn't available to listen to or purchase online until tomorrow.
George FM issued its own ultimatum to DJs over the single, warning them not to criticise their colleagues, or face being taken off air.
"As a direct requirement for anyone wishing to maintain a show at this station, ANY and ALL social media relating to the new George FM Night time residents and schedule must be positive," it said.
George FM DJ Aroha Harawira spoke out in support of Key, saying he should be judged on his musical ability and not his father's politics.
"I haven't met Max Key yet myself, I've never seen him DJ, but I heard him on George FM last night and I thought he played a pretty sweet set," Harawira wrote on her blog site.
"I value my friends' opinions and I'll give the guy a chance. I think you should too ... Say what you want about John Key, but leave his kids out of it."
In a review for the Herald, critic Steve Braunias said Max Key remained strangely silent during his radio show. His first words - "Thanks, bro" - didn't come until 26 minutes into the broad cast.
"He kept his head down. He sounded like a nice guy, laidback, no one special ... He wasn't killing it. He was kind of chilling it. He sounded like a man quietly determined to have a party, and it made for a pleasant hour," wrote Braunias.
Read more: Steve Braunias on Max Key: 'He wasn't killing it, he was chilling it'
- nzherald.co.nz