As I read Eph. 4:15, "Speaking the truth," I find it would be better translated as "Holding," that is, holding the truth in love. In the Greek, Paul's word here (aletheuontes) literally means "being the truth" that is to say being in ourselves the embodiment of the Christ we represent. And you are right, in that the end is the seven fold unity of the spirit. Vitriolic denunciation may well serve the unsaved in politics but our best weapon in Christian discussion is truth dripping with tears of loving concern. And above all... Grace!