Not that directly, but saying they have “zero worth” might be against GG Article 1

Human dignity is inviolable

Pretty sure dehumanizing can be prosecuted under this, even if its rather tame. Also there have been some laws over the last few years that criminalize violent speech on the internet and that give people the ability to report comments directly to agencies. These might make it quite dangerous for the instance to keep up these comments.

I assure you, German leftist often say way more intense stuff on a daily basis, but not on publicly hosted servers

feddit.org is a German hosted instance that has to abide by the German law. By that law, your comment falls into a grey-zone of legality. As much as I agree with you, they were right in removing your comment, as they are legally obligated to. They could get into trouble if they don’t.

To quote the feddit.org sidebar:

Content that is illegal in Germany, Austria or Switzerland will be deleted and can lead to an immediate ban of the account.