DMCA safe harbor means you don't get sued for posting copyrighted content. But in return it means you get a notice you gotta take things down. If you don't take it down then it goes down the infra. You can take down a post but your hoster can't. But they can take down your server. And they must or they get fines/jail. And so they will.

Now we need to know the full story. Did you have a public DMCA takedown link and actually handle requests and the complainers just ignored that and went over your head to Herzner? or did you just wing it running a server with UGC thinking it's surely gonna be OK?

I am not saying you were wrong but you only tell a small part of the story