Why heart?

D: Sir Oda Eroichiro, greetings. Why did Caesar demand to have Law’s heart? Logically speaking, I feel like his dick would be so much more of a vital body part to lose.        P.N. ikeyan

O: …Hum. Indeed… the willy (classy) would also be a vital body part. However, how would the imagery turn out looking like? Law holding his willy, and Law holding his heart. Which has the better impact…? For instance, Law… They say that he, in order to join the Shichibukai, delivered 100 hearts to the Marine Headquarters… But… if he had delivered 100 willies instead, by now, Law would have become a Shichidikai.