You are wrong.

Disagreeable individuals place self-interest above getting along with others. They are generally unconcerned with others' well-being, and therefore are unlikely to extend themselves for other people. Sometimes their skepticism about others' motives causes them to be suspicious, unfriendly, and uncooperative. People very low on agreeableness have a tendency to be manipulative in their social relationships. They are more likely to compete than to cooperate.

Do you have any actual knowledge of the Big Five psychometric scales, or are you just saying that because you want it to be true?

Disagreeableness is a scientifically validated and incontrovertible synonym for meanness.

Agreeableness is a personality trait manifesting itself in individual behavioral characteristics that are perceived as kind, sympathetic, cooperative, warm and considerate. In contemporary personality psychology, agreeableness is one of the five major dimensions of personality structure, reflecting individual differences in cooperation and social harmony. People who score high on this dimension tend to believe that most people are honest, decent, and trustworthy.

Agreeableness is a synonym for niceness.