If the board deems it for the best interest of the district that the lands mentioned in the petition for exclusion of lands, or some portion thereof, be excluded from the district, and if no person interested in the district shows cause in writing why such lands or some portion thereof, should not be excluded from the district, or if, having shown cause, withdraws his objections, or upon the hearing fails to establish such objections as he may have made, the board may, by unanimous vote of all of its members, make an order that the lands mentioned and described in the petition, or some defined portion thereof, be excluded from said district.
The board shall order the exclusion of all lands petitioned to be excluded from the district which, in the judgment of all of its members, will not be benefited by the operations of the district.