I think you're right. We don't want to be banning books (in the sense of forcibly preventing their publication.) We can limit them in the sense of not subsidizing them, e.g. not using public funds to purchase them for schools, libraries, people in jails and prisons, etc.
Certainly there are "powers that be" who would like to ban the Bible as well as the Quran, and who would use the German proposal as an obvious and almost irresistable pretext.
In fact, in Canada teachers have been fired from their jobs, and people have been investigated and punished for "human rights violations," merely for quoting from the Bible--- in speech or in print --- on the subject of homosexuality.
Book-banning can't work in a society that has hundreds of millions of books in print, and well-nigh universal Internet. The Qu'ran doesn't need to be banned. It needs to be openly refuted, repudiated, and de-legitimized.
I completely agree. Unfortunately, it looks as if the press and academia will not delve into the koran willingly so I suspect the Bundesverband der Bürgerbewegungen is taking it to the courts as a means of forcing the discussion into the public arena.