The scene from Disney's "Dinosaurs" in which the Carnotaur kills the Ceratopsid may help us ,if what we want to think about is only some kind of offensive behaviour using the horns; these horns are laterally directed (cranio-laterally?). In the scene the theropod runs from the back of the Ceratopsid, and reaches it , pushes it down by one side, using its body weight and then kills it..This is obviously speculation, but not an unlikely scene IMHO.
If the horns were covered by keratine(?) ,so that they would have been longer and sharper than the simple bone, then it would have been quite easy to inflict a severe wound in the body of the attacked animal before pushing it dowm, by means of a violent laterally directed movement of the head-neck[ thus avoiding the use of a pretty weak bite(if it really was weak)].I don't know if the neck (or the same skull)would have been strong enough to bear such a violent impact, but ..
just a thought...