Well, if I take my English's dictionary :

Arrogance : 1. offensive display of superiority or self-importance; overbearing pride.

Humble :
1. not proud or arrogant; modest: to be humble although successful. 2. having a feeling of insignificance, inferiority, subservience, etc.: In the presence of so many world-famous writers I felt very humble. 3. low in rank, importance, status, quality, etc.; lowly: of humble origin; a humble home. 4. courteously respectful: In my humble opinion you are wrong. 5. low in height, level, etc.; small in size: a humble member of the galaxy.

Considering humility is the supposed opposite of arrogance, I am assuming that humility mainly imply inferiority which means that it isn't really a good behavior either.

Rationally speaking if arrogance is 10 and humility is -10 wouldn't 0 be the rational answer as of how to act considering the society seems to value humility due to the desire or rather good feeling humans feel when someone act as inferior toward them ?

If the above is true it means that both humility and arrogance are "bad" and should be seen from a different perspective.