IDK i don't see this stuff as all that different from doing like a k-means clustering or factor analysis on a data set, it's just an attempt to do it on human personality, which we know has variance and correlations. We don't freak out at market segmentation analysis that involves labels like "early adopters" and "laggards" which are imperfect but informative.
I think people just find the entire idea of labeling humans in this way offensive, and latch onto some of the claims that it's "science" as an avenue of attack.
Edit: And I think it's slightly better than just categorizing people based on their birthday like you do in Astrology, as you are using at least responses to a personality test in most instances.
Personalities doesn't cluster so k-means would not give anything interesting. Big 5 is pretty close to a factor analysis on a questionnaire data set though, so that's a reasonable though. Four colours is not based on anything like that though.
I'd say that astrology is better than DISC in that it's obviously bunk, the problem with the colours is that while some people claim to enjoy it as a pastime or conversation starter, some seem to take it further and base actual decisions on it. People reading horoscopes in a magazine wouldn't typically actually follow the advice therein.
I think people just find the entire idea of labeling humans in this way offensive, and latch onto some of the claims that it's "science" as an avenue of attack.
Edit: And I think it's slightly better than just categorizing people based on their birthday like you do in Astrology, as you are using at least responses to a personality test in most instances.