One of the favorite pastimes of modern Americans in general, and many Christians in particular, is judging or criticizing others. We seem to relish the opportunity to find fault, assign blame or just plain criticize others. This is so common in everyday conversation that it is like a plague in the social system of our culture. This may be one reason why I think we handle politics so poorly. I know this is why we handle a lot of theological differences so badly. We believe that we must be right and thus the other person must be wrong. We then reason that we have a right, indeed a responsibility, to discern what is wrong and thus we judge/criticize the person (people) who teach what is wrong.
I think we can safely summarize the biblical teaching regarding criticism in the following way: God's people are to exercise judgment in legal and church matters (cf. Dt. 16:18-20; Lev. 19:15; Ex. 23:6-7). And true judges are appointed by God (1 Kings 3:28; Ex. 18:13-16; 1 Samuel 7:15; 12:1-4). Believers must also exercise personal judgment with regard to matters that involve their conscience and their personal choices. (We will all answer to God in the Last Day.) This is why we can, and sometime should, disobey government(s) or rulers. But we must always be careful to "judge justly." But, and this seems very important to me, the primary emphasis in Scripture is on fairness and impartiality, traits all too often missing in modern dialogue, writing and criticism. The temptation to "pass judgment" on a person's life or on the testimony of other individuals is clearly warned against in Scripture.
It seems clear enough in John 8:3-11 that our Lord refused to judge the woman actually caught in the act of adultery. And Luke 12:13-14 indicates that Jesus was not sent to judge in his incarnate mission, which was one of salvation and service. (He will judge in the final day!) Add to this the evidence of John 8:15-16 and then that of John 3:16-17, which sums up Jesus' response to judging the world now. He came to "save the world," not "to condemn it." ("World" here clearly means the world of people and likely means even more; i.e., the whole created cosmos.) It becomes apparent, when you read the New Testament, that the early church did not spend much time condemning the (Roman/Greek) world but rather spent its energy on loving those who were outside the kingdom of God and seeking to transform them and the surrounding community by the power of grace and the gospel. (The church did instruct disciples in how to avoid the temptations of the world's system, or its fallen way of thinking.)
But correct discernment is commended to Christians. 1 Corinthians 5:12-13 indicates that we are not to judge those outside the church but the church (this is the context of the epistle) is to judge its own members. We reverse this in almost every modern instance I know. We encourage continual verbal attacks against the world, thus many find the church hypocritical for good reason, while within the church we tolerate gossip, slander and malicious judgment as normal (Cf. also 1 Corinthians 5:1-5; 6:1-6).
What I have said does not preclude judging ministries carefully. (Every donor should do this as wisely as possible!) Matthew 7:15-20 provides the basis for us to ponder this sobering truth, as does 2 Corinthians 11:10-15.
But all of the above is a far removed from 99.9% of the criticism that I hear and read on a daily basis among Christians. (Blogs can be the one of the worst places for this to happen, which drives me to pursue a standard that is higher, even if I sometimes fail.)
There is a positive type of criticism, such as that found in a book review or an article that exposes truth factually with a minimal amount of condemnation regarding motives, etc. But harsh criticism is out of place. Nastiness is always wrong. Undercutting a person's life and integrity, with false accusations, is always wrong. The reason that we do this, I have become convinced over the years, is because we need a way to bolster our own ego and to assuage our human fear. We feel better, at least for a time, if we can show that someone else is wrong. We feel stronger and more secure if we are right and someone else is clearly wrong. But the apostle John says, "perfect love drives out fear" (1 John 4:18). And perfect love is always the goal for a mature Christian, not perfect doctrine and perfect arguments.
It seems obvious to me that most of what we call necessary and biblical criticism is just wrong. James 5:9 says: "Don't grumble against one another, brothers and sisters, or you will be judged. The Judge is standing at the door." I take it that our judging of one another actually invites God's judgment as he stands right at the door of our lives, our churches, etc. (This is an obvious metaphor, much like Revelation 3:20.) I also take it that one of the major reasons why most all of our churches experience a major power outage of spiritual reality can be found right here. God has judged our churches because they are judgmental societies that do not do his work in the world.
The bottom line here seems self-evident. We are never to judge the world. Christ will do that in the last day. We are to judge believers when the whole church (at least the local congregation at a minimum) is involved. Heresy has not been proven to be true just by using the word on a Web site or blog. We can and should be discerning about our personal stewardship and conscience when we make choices. But criticism is, in general, a lot like fire. It can be a useful thing if used correctly but it can also burn down homes and destroys lives when used by irresponsible adults or little children. There was a campaign some years ago which suggested we should not let our children play with matches. I would suggest the church begin a campaign that says, "Don't let your flock handle the matches of criticism or you and your ministry will be torched by the damage!"