In Germany it's often illegal to make strong statements like this unless they can be proven beyond a reasonable doubt. Is that the case?

(That's partly why Germany is getting infested with Nazis again. You can go to jail for calling them out.)

It's a civil matter, but yes. Sadly, courts are slow and the whole story was "there might have been plagiarism in her thesis". Even as traditional media started to explain the story as baseless, social media is a different beast.

Can you provide some sources to back up your claims?