That ever-popular Epistle of St. James--one of several New Testament books our good friend Martin Luther would have felt just as comfortable without it being in the text. Here's what James says of the tongue:
James 3: 8-12
8But no man can tame the tongue. It is an unruly evil, full of deadly poison.
9With it we bless our God and Father, and with it we curse men, who have been made in the similitude of God.
10Out of the same mouth proceed blessing and cursing. My brethren, these things ought not to be so.
11Does a spring send forth fresh water and bitter from the same opening?
12Can a fig tree, my brethren, bear olives, or a grapevine bear figs? Thus no spring yields both salt water and fresh.
Heading straight back to my theme--when we use a label to demean a person--to, in a sense, curse the person with the label itself, are we not cursing ourselves with the judgment we have wrought?
Some argue that we can know that a person lies. He can even know that the person lies habitually. What of it? Are we so pure that we can point to someone and with impugnity call him a liar? What do we do when we commit this act? In a sense we violate the spirit of the person so that we can lord it over them. Most labels serve a single function--to exalt ourselves at the expense of another.
James goes on to say this:
11 Do not speak evil of one another, brethren. He who speaks evil of a brother and judges his brother, speaks evil of the law and judges the law. But if you judge the law, you are not a doer of the law but a judge.
12 There is one Lawgiver, who is able to save and to destroy. Who are you to judge another?
To my mind that suggests false and easy labels. Someone tells you a lie. Does that make a person a liar? Absolutely. It does not make that person an habitual liar, but it certainly merits the label by definition. What do we get from labeling the person a liar other than a judgment stamped against us that labels us a hypocrite or worse yet, a judge of others? Have we some harvest of truth in labelling the person a liar? Has the cause of charity and the redemption of the transgressor been advanced?
Judgment is reserved to God alone. We have no right. When we assume the right, we usurp God's own power and become blasphemers. Many of our labels are a short-cut to judgment.
A person tells you a lie. You have several choices about how to respond to the matter. Let's assume that you decide to call them on it. Among your choices of repsonse are: "You are a liar." (Just the tone suggests both anger and judgment--at best an unhealthy combination.) Or, perhaps, "That is a lie." (Said in some degree of directneess.) Now the person can turn back to us with the second statement as say, "Are you calling me a liar?" And the absolutely truthful answer is, "No, I am saying that the statement you made was a lie." There is a difference, and the difference is enormous. In one case we are judging and discerning an isolated action--not the whole person. In the first case we have judged and condemned the person by applying the label.
Some will argue that there is no condemnation in calling someone a liar. But I would ask, if not, why do so? How is the action any different than saying, "What you said is a lie." The fact of the matter is that we know the difference to the core of our being. Calling someone a liar allows us to express our "righteous indignation" against such a profound transgression of God's peace and love. Not that we would ever consider so violent an act against the kingdom. Saying that a given statement is a lie is an objective verifiable or falsifiable statement regarding an action. It condemns the transgression without condemning the transgressor.
At what point does one who tells lies become a liar? I would suggest that it most often occurs when we get angry enough to apply the label. Is anger ever a good reason to do anything? Is calling a person a liar an act of love? I would submit that it is not. I would suggest that saying, "You tell a great many lies," summarizes the truth without the sting. That said, I will open the door a very small amount to say that it is conceivable that in order to be shocked out of behavior the stronger language may be used, but never as it is commonly used and only in the hope of correcting the fault. Hence, the frequent labeling (though almost never of individuals) in the New Testament Epistles. The point here is to use violent language that shocks the person out of his or her habitual slumber. So it is conceivable that you may call a person a liar and not be sitting in judgment, but only if this is done in charity to the person himself. Too often we apply our labels to persons "behind their backs." Rarely are we brave enough to say face to face, "So and so is a liar." More often we say to another , "He's such a liar." In which case we commit the grave injustice of gossip and rumormongering. This person is not present to defend their statements or their integrity. We are condemned by our own backbiting.
So I would say that the most general case calls us never to label, never to judge a person. It calls us equally to challenge those we see going astray by pointing out the actions that transgress, being always mindful about how we do so. Our goal is always charity and must always be the reformation of the sinner. (This label has a certain biblical and Traditional authority for all of us.) I think we should strive to correct the erroneous behavior--a goal that is rarely accomplished by verbally assaulting the person committing it.