They tried that before, the Verfassungsschutz will say, publicly, something along the lines of “Two of these 500 quotes are from our moles”. That way they protect their sources, vanishing in the general soup, while the court can see that it’s party sentiment, not something injected into the party by the Verfassungsschutz. Judges will be able to see the whole uncensored thing one way or the other though it might not necessarily the judges actually judging the case: There’s special in camera senates in high courts for when some agency really doesn’t want to show stuff. They can look at absolutely anything, and all they have to judge is “yep, it was indeed 2 of 500 quotes”.