Whenever the board shall find, as part of its findings of fact in any proceeding before it, that the party or parties filing charges of unfair labor practices upon which the complaint was based have engaged in an unfair labor practice (as defined in section six ) in connection with or as part of the actions forming the basis of the complaint, such findings shall constitute a complete defense to the complaint, and no order shall issue thereon against the person charged.
43 P.S. § 211.10.1