Why does goemom tell manjiro that he can never be a samurai?

Goemon told Manjiro he can never be a samurai for he did not commit harakiri, which is a form of self-mutilation and su^cide so as to escape being captured by enemies. Japanese Samurai status is achieved only when a person braves the odds and prefers to die instead of being taken captive or even killed by an enemy.

Explanation:

The reason Goemon thinks Manjiro is not a true samurai is because, for him, since Manjiro did not commit su^cide or harakiri (seppuku), he did not deserve to be considered a samurai. He did not like the idea of Manjiro being taken to America, stayed there for almost a decade, and returning back and being honored with the samurai status.