I’ll give it some thought. In essence, the ninja grew out of the poor people who had their goals but could not complete with the well armed and trained Samurai.
When needs and goals conflicted between the establishment served by the honorable Samurai and the poorer classes, they were forced to train as night fighters to stealthily sneak up and attack.
Different people with different needs, both competing to attain their goals as best they could, neither being morally superior to the other.