It may shock you to learn that countries exist outside of the US, and they have different laws. Notably, Germany (the place in question) has copyright enforcement with actual teeth.
You quietly comply. Then take tougher security measures to protect yourself before continuing. Do not respond under any circumstances. If you’re served with actual legal papers, retain an attorney.
I have received a copyright infringement alert, what should I answer? (i.imgur.com)
(Of course I’m going to stop, but my server has been blocked by Hetzner, would like to recover it XD)