At the hearing, testimony may be presented by all interested persons in support of, or in opposition to, the establishment of the district, the extent of the district, the proposed rehabilitation program, or the proposed method of financing that rehabilitation program. The city or county officials responsible for the construction or maintenance of the public facilities proposed for rehabilitation shall testify with respect to the need for rehabilitation, the scope of rehabilitation required, and the cost of performing the rehabilitation. Any protests pertaining to the regularity or sufficiency of the proceedings shall be in writing and shall clearly set forth the irregularities and defects to which any objection is made. All written protests shall be filed with the clerk of the legislative body on or before the time fixed for the hearing. The legislative body may correct minor defects in the proceedings at the hearing. Written protests may be withdrawn in writing at any time before the conclusion of the hearing.