Well, here's why the word "weeb" isn't racist.
1. Otakus are people who like anime, manga, video games, technology, and other stuff related to that.
2. Weebs are people who like anime and manga, but may not always be passionate about the other things.
3. "Weaboo" would be the more offensive one. Just plain "weeb" isn't intended to be mean; "Weaboo", on the other hand, is.
4. Otakus are more like hard-core weebs, basically veteran weebs.