Any report published in any newspaper of the proceedings of a public meeting shall be privileged, if such meeting was lawfully convened for a lawful purpose, and open to the public, and if such report was fair and accurate and published without malice, and if the publication of the matter complained of was for the public benefit; Provided always that the protection intended to be afforded by this section shall not be available as a defence in any proceeding if the plaintiff or prosecutor can show that the defendant has refused to insert in the newspaper in which the report containing the matter complained of appeared, a reasonable letter or statement of explanation or contradiction by or on behalf of such plaintiff or prosecutor.