No association as defined in this Act engaged in any of the activities herein, shall be deemed to be a conspiracy or combination in unlawful restraint of trade or an illegal monopoly; or an attempt to lessen competition or to fix prices arbitrarily, nor shall the marketing contracts and agreements between the association and its members or any agreements authorized in this Act be considered illegal as such or in unlawful restraint of trade or as part of a conspiracy or combination to accomplish an improper or illegal purpose.