The ancient Romans believed in many gods, and their chief god was Jupiter. The title they gave Jupiter was, in Latin, Conservator, or savior. Salvation, in the pagan mindset, consisted in the conservation of Rome: the preservation of the status quo of Roman society. For Christianity, our God, who is also a savior, is not a conservator—one who preserves the particular society—but a salvator—one who renews and transforms society. The Church, the Body of Christ the savior, is always moving forward, renewing and transforming herself. This is why we qualify our history as salvation history. The Church is not related solely to the past, but lives in the present, bearing within itself the character of hope and pointing to the future.
The Church may have had negative moments in history: the Crusades, the Inquisition, the trial of Galileo, etc. But the fact that the Catholic Church is continually progressing forward and fulfilling God's will means we cannot be an evil or false institution. We have renewed and will continue to do so. To those who doubt this, or have left the church because of some past blemish, like the Borgia popes, need only take the example of the most recent crisis and, I would argue, the darkest moment in the Church's history: the sexual abuse of children by clergy. This was an evil committed by the Church, and yet I or you reading this would not say the Church is evil or a false institution. We still believe in Catholicism and receive the sacraments despite this fact. That is because we know, in a faith founded on the Resurrection, that evil does not have the final say. Our active Catholicism right now is living proof that Christ is alive and in his Church. We are the empty tomb.