Kabuto being compassionate in general is a very strong word to use, maybe compassionate about avenging Orochimaru, becoming strong, selfish reasons like that etc.

We've seen before that Kabuto never gave a crap about anyone except perhaps Orochimaru, and laughed in the faces of despair around him. He's always seemed strong, but not any natural type of strong like anyone else, the type of strong that he somehow got through cheating/conniving.

If Kabuto hasn't totally lost it by now, then he is no longer held by the boundaries of what is logical to the average ninja (if he ever was), lol if that wording makes it any better.