a majority of his/her subject matter are western characters, labeling it western makes it so that people searchin for western characters can find it, so relax, no need to call names
Uploaders already screwed up and put some of his work under Western. If people are searching for western content by Japanese artists, they'll use the specific tags of the content they're looking for, not a generic "western" tag; never mind everything tagged as "western" in Doujinshi and Manga is just Western stuff under the wrong heading. But mis-tagging it won't change the main section heading, so whatever.