"We see in the rapper scene, and increasingly also with other influencers, that they are sometimes very negligent with their influence."
Supporters of rival social media stars fought each other in a mass brawl in Berlin's landmark square Alexanderplatz.
Police made nine arrests after 400 backers of two German YouTubers squared off on Thursday evening.
One of the stars, Berlin-based Bahar Al Amoodm, who has 13,000 subscribers on the video platform, later apologised. His rival, ‘ThatsBekir’, from Stuttgart, said he needs to take a break as a result of the fracas.
"We see in the rapper scene, and increasingly also with other influencers, that they are sometimes very negligent with their influence," said Norbert Cioma, head of the Berlin chapter of the GdP police Union
"It seems to be fashionable to deliberately open a powder keg to generate more followers, subscribers and clicks."
Officers used tear gas to clear the square but the fight then continued in a subway station when around 20 people threw rocks at each other, a police spokesman said.