https://www.lhr-law.de/magazin/social-media-recht/olg-dresde...

It’s not surprising this exists. It’s equivalent to the Hausrecht in the physical world - if you make your place available to the public (a bar, restaurant, supermarket) you no longer can kick out just anyone without cause. You can ban people from entering (or make them leave) for reasons, but those must be non-discriminatory and not arbitrary. “I don’t like you nose/hair/color of your skin” won’t work. “You need to wear shoes or leave.” is likely valid.