Hello, ladies and gentlemen. I hope you don't mind me giving some input.
smile The first thing to remember is that racism is rarely intended. The most pervasive and pernicious form of racism is unintended racism; the kind that makes people freak out and go "But I didn't mean it that way! You're being too sensitive!" when you point it out to them.
Now that we've got that out of the way, I think it's important to put Sailor Moon into its proper context. Sailor Moon is set in 90's Japan, and Japan is not a country crawling with minorities - only 1.5% of the population comprises of racial groups other than Japanese. Thus, a multiracial cast of senshi would be forced at best.
(Sailor Pluto does not count as any race other than Japanese; despite her somewhat darker skin, her facial features are clearly drawn to look Japanese and she does nothing that sets her apart culturally from the other senshi.)
On the other hand, the villains have far more diverse backgrounds. Yet they all appear Japanese. (Anyone who argues that you can't tell what ethnicity an anime/manga character is supposed to be needs to watch anime more carefully; Western characters are indeed drawn differently. Just look at the episode with Sailor Venus in Britain; Alan's English ethnicity is very much apparent in the way he's drawn.) Even villains that come from other planets appear Japanese. This is indeed racist - the kind of racism that makes people think of their own race and culture as "normal" and everyone else as the outliers. It's not
intentional racism, but it's still racism. Even Al, En, and Fiore, who are the most "alien" aliens in the anime, look Japanese.
The creators of Pretty Guardian Sailor Moon made a very racially-unfortunate casting choice when they chose half-American Alisa Durbrow to play villain Kuroki Mio. The Japanese are already xenophobic enough as it is; having the
only regular character who obviously wasn't full-blooded Japanese also be a villain was a very poor choice, similar to how American writers relegated foreigners to exotic villains. It only confirms in the subconscious minds of viewers that those who look foreign are evil and cannot be trusted.