Eccentric isn't negative

I thought that the Summit ESL book was great, until I saw that they define the word "eccentric" as a negative personality trait. They had a list of traits to demonstrate different kinds of adjectives, and they separated them into two lists. Eccentric went into the negative category. That is absurd. According to the dictionary, it means deviating from a norm, convention, pattern. So I guess we can conclude that the writers of that book are bland conformists. Or people who are unable to distinguish between disturbing difference and noticeable individuality.