The notion of a prosecution must surely have been one of the stupidest ideas put forward by anti-religious extremists. I haven't read the book but from what I have heard it is a valuable academic theoretical discussion appropriate for yeshiva bachurim who intend to do army service, about the parameters of when it is permissible and when it is not permissible to kill - beyond the obvious simple situation of a person right in front of you threatening to kill you. There is nothing racist or potentially violent per se in having such an academic discussion on what halacha has to say on such matters. The instigators of the petition are purely anti-religious trouble makers.
German authorities accused of playing down refugee shelter sex crime reports (Reuters)
from the article: Israel's AG closes probe into authors of allegedly racist book