It is the public policy of the State of California that manpower should be used to its fullest extent. This statement of policy compels the further conclusion that human beings seeking employment, or retention thereof, should be judged fairly and without resort to rigid and unsound rules that operate to disqualify significant portions of the population from gainful and useful employment. Accordingly, use by employers, employment agencies, and labor organizations of arbitrary and unreasonable rules which bar or terminate employment on the ground of age offend the public policy of this State.