The complaints about promoting magic seem very strange on the surface but if you get inside their worldview it suddenly makes a fair degree of sense.
People that object that these sorts of books promote magic are almost always extremly conservative christians. These are the sort of people that believe that God takes a direct hand in manipulating this world, that prayers can cause God to take action, and so on.
The obvious counter point to that is that they also believe that you can invoke the other power also. And since, in their world view, there are only two powers, if your not invoking the first you must be invoking the second.
They think books like this are dangerous for exactly the same reason we would think a book showing kids being raised in a Nazi boarding in a positive way would be a bad thing.
The faults of this world view are many, but from their world view it is certainly self consistant and resonable.
Jay