Thanks, Rejo (and others) for elucidating the point. I now get your line of thought.
I learned that the qualification "not select or modify" acually IS present in German law. ยง 8 TMG says, that the service provider is not responsible in so far as he did not "chose or modify" the transmitted information.
Although, the greater risk in my opinion, comes from the question if tor operators can be seen as service providers who would be exempt from responsibility for transmitted information under the term of this law. There's no precedence to my knowledge, but private wireless APs are in fact not exempt from responsibility. I'd rather pessimistically guess that most courts would judge tor operators in analogy to people operating private open wireless access points ...