Faith is easily hollowed rather than hallowed; the course of sloth and pride lead to advocating virtue to others while avoiding it ourselves. The most grievous sins seem to be those in which others indulge; while our own, though regrettable, carry less of an affront to nature. Thus, the obligation of witnessing devolves into denunciation, erecting barriers between people designated "good" and "evil". Condemning others often leads to a spiritual blindness, the intoxication of self righteousness numbing senses to shortcomings much closer to home. Energy devoted to exposing failure in others becomes paramount; self improvement resources are greatly diminished and deemed of secondary importance.
Faith serves best when it compels action within, rather than censure without; the most effective method of changing the environment involves expending moral capital upon ourselves. There is little enough power allotted to mold the person over which we have the most control, ourselves, to afford us the luxury of changing others. We suppose that, in our wisdom, we can best choose the course of neighbors when navigating our own way is job enough for many lifetimes. Perhaps it is the distraction of judging others that we use to hide from our own responsibilities; much more pleasant to focus on anything but the primary task at hand.
The worst aspect of castigation lies in its role in moral erosion; indulging in the debasement of others saps the will to create positive change, and leads to a degradation of faith. Raising self can't come at the expense of lowering others; in the end, all become dragged down. Aiding others by a demonstration of virtue is far more instructive, if far more difficult; but it is the effort that makes the task worthwhile. By effecting self improvement we not only show the strength of our convictions, but infuse ourselves with the virtue we claim to value.
Faith of our fathers, we will love
Both friend and foe in all our strife;
And preach Thee, too, as love knows how
By kindly words and virtuous life.