How not to be a racist douchebag for Halloween

A rather good series of posters featuring Halloween costumes that people really should have thought twice about wearing, under the slogan "We're a culture, not a costume":
Blackface? Seriously?
Suicide bombers, geishas, and sombrero-wearing dude (burro included)
Native Americans

I do find it interesting that my reaction to the geisha costume was more muted than my reaction to the others. I mean, if somebody suggested to me that I dress up as a geisha for Halloween, I'd probably say, "Nah, that wouldn't feel right, and anyway, I'd rather be a pirate or a steampunk gothic cowboy or Joan of Arc." (Nevermind that my usual Halloween costume these days is "person who couldn't be bothered with a costume") Whereas a suggestion of any of the other costumes depicted would be met with a "Wow, that's so offensive, I can't believe your head didn't catch on fire the moment you thought that." This may be a cultural blind spot on my part.