If the boss at Billy Bat World hates the Japanese, how does he know a Japanese comic's called a manga?
Translation error. Manga literally translates as "comic." The translators didn't catch that. Shame on them.
I've noticed that error several times. Of course, it's tricky to know when to use the word "manga" in the translation and when to use the English word "comic," but when an American is talking about an American comic book they should always use the word "comic," and yet they sometimes write "manga."