"Prejudice" literally means "pre-judge," (hence the linguistic similarity) so it's not just a synonym for disapproval. Disapproval based on skin color is automatically prejudice because someone's skin color is not indicative of their character.
Thing is that statistically, a person's skin color is indeed indicative of a person's character. In the US, a black man has 8 times higher probability of being a criminal than a white man. And on average an Asian usually has 20 points of IQ more than a black. And as Captain Steel has shown, it's common for blacks to feel discriminated when someone doesn't like rap.
So ethnic groups differentiated by phenotype have certain characteristics that hold on average.
Disapproval of general cultural tendencies isn't inherently prejudiced because it's based on actual choices. And if you can't have negative opinions about people's choices, you really can't have negative opinions about anything.
So you wouldn't think that a person's opinion regarding "general cultural tendencies" of a culture he/she does not know anything about to not be prejudiced?
Also it's very, very hard to identify a "general cultural tendency" in a large country. When people think in terms of general cultural tendencies (such as "all Japanese comics look like "this") they are engaging in stereotyping and that's inherently prejudiced, it's the same as thinking that blacks are lazy.
Take the US, are there very clear "general cultural tendency" in the US's culture? Well I wouldn't think so. American music, for instance, contains pretty much any genre of music in existence in the whole world, if you dislike "American music" you dislike music, unless you redefine American music to mean something very restricted like "rap". Same with Japanese comics, well, even more considering Japan makes the vast majority of the comics in the world: if one dislikes "Japanese comics" one dislikes comics.
Unless you redefine manga to mean "action fantasy manga published in Shounen Jump magazine", which is most Anglophone people's idea of "anime" actually but that is as representative o "anime" as 50 Cent is representative of American music.
Originally Posted by Captain Steel
My point is - disliking anything in the realm of media, arts or entertainment, doesn't mean you dislike an entire country's culture, nor an entire race's, ethnic group's, regional group's, religion's, or orientation's culture either.
Of course, if you dislike a movie like Your Name (2016) that doesn't mean you hate Japan. Or even if someone says he/she is not going to watch Your Name because he/she did not like the art style used in that movie.
However, if one says he/she is not going to watch Your Name BECAUSE it's Japanese, then, I think that we have a problem: Modern Japanese visual culture is not like rap, rap is a genre, it's a clearly defined defined genre of American music with very clear characteristics (such as lack of melody and harmony you just mentioned). People here think of Japanese comics as if it were like rap but it's like American music, and it's impossible for me to conceive that someone might dislike
all American music just as its absurd for me to think of someone who might dislike
all Japanese comics. I don't think it's actually useful for people to use terms like "anime" and "manga" because they create artificial stereotypes that only exist in the heads of westerners.