Realizing that the book burnings in the 1930s were not performed by the dumb Nazi brutes we know from movies like Indiana Jones, but by student organizations (e.g. what should be sufficiently smart people) was a bit of a shock to me (not really anymore from today's point of view seeing how easy otherwise smart people get themselves into a spiral of hate and fascist ideology).
So, it was smart and young German students that wanted to get rid of most or all of the material produced by one of the earliest institutions on the planet dealing with controversial topics like birth control, LGBT, fetishism, sadomasochism and venereal disease.
The founder and most of the researchers there were Jewish, so I wouldn't discard an antisemitic motive behind that as well.
As you say, I always bought the "dumb nazis burned books" story, but this context makes me think about the event in a much different way.
