"Hmmm." The Commander looks ponderous for a moment. "That is a wise thought. You are catching on to this. Maybe, if we were talking of Arrancars of the past, I would agree with you." Li takes the paper and draws a small, misshapen Arrancar exactly where Koutarou pointed.
"But after listening to the Arrancars speak, can you still say they lack a purpose? Let's engage in speculation for a moment and assume their leader was being truthful. They are building a city. They want to play their part in this world. They want to be like us."
Li draws another Arrancar, this time dressed in an uniform similar to the Shinigami - only the colors are inverted, with the Arrancar being white where the Shinigami is black.
"It took a long time for us, too, to realize our purpose. What you said about Arrancars being dangerous is true - but the exact same thing can be said of a Shinigami without purpose. You know what Sabitsura Sho is like. The Academy was founded to reel in people like her. Kiba, Sawada and many, many others - were just like her. Just like a human grown among wolves never learns to speak, a Shinigami lost in Rukon never grows to be more than thug with superpowers."
Once again, Li presents the picture to Koutarou. It's now complete with a caricature of Sho below the Shinigami. "After hearing what I just said, would it surprise you if I told you Arrancars have more in common with Shinigami than either have with Pluses or Hollows? Not in some abstract manner, but physically. In the way their bodies are shaped, in the way their bodies work?"