It is common nowadays to hear Christians say that the church and individual Christians should "speak prophetically" to the world. By this they mean to speak what God would have them to speak, and not necessarily to predict the future. Thus it is common to hear Christians claim that they are "speaking prophetically" when they say something which they believe God would have them to say, such as publicly calling a sin and a sin despite the world regarding it as no sin.
Sad to say, it is also common nowadays to hear Christians play the prophet: that is, to make a pretense of speaking prophetically. Based upon my observations, I think in most cases--possibly all--a person who does this is unaware that that is what he is doing: he really believes that he is speaking prophetically, even when the world recognizes it isn't. He thinks he is serving God, but is actually doing Him a disservice by bringing Him and true prophetic speaking into disrepute through the pretense--which the world may immediately recognize as pretense.
One of the ways one can recognize whether someone is playing the prophet is by examining whether he is applying a moral standard consistently. If we see that he does not, that is reason to be concerned that he is playing the prophet.
By way of example, following is one common way in which Christians in America play the prophet nowadays:
When a politician who is on "the wrong side" commits a scandalous sin
"As God called Elijah to rebuke and denounce Ahab, and as God called John the Baptist to rebuke and denounce Herod, I, as a Christian, am called by God to rebuke and denounce this man for this scandalous sin. Even if the sin does not bear directly on his public office, we should still be troubled by it, because a man's character cannot be divided between private and public. If he can't be trusted in private matters, how can he be trusted in public ones? Character matters. If a politician doesn't have a good character, nothing else matters. This sin disqualifies him from holding public office. God is a God of righteousness and justice, and we should respond to this sin and the man who committed it with righteousness and justice. I call on my fellow Christian to join me in doing so. If he won't leave office voluntarily, then we should see to it that he is removed."
When a politician who is on "the right side" commits a scandalous sin
"As a Christian, it isn't my responsibility to judge and condemn. That's God's. No one is perfect: we're all sinners--him, you, me, everyone. As a sinner to whom God has been loving, gracious, and forgiving, I am to be loving, gracious, and forgiving toward fellow sinners, including this one. If the sin does not bear directly on his public office, then it should not disqualify him from holding that office. What matters is policy: whether his policies as a politician are good or bad. And even if it does bear on his office, God can still use him for good--just like He used King David for great good although he committed great sins. God is a God of mercy, and His attitude toward this man is merciful, despite whatever sin he may have committed. As a Christian, that's my attitude toward him, too. I ask my fellow Christians: rather than criticize this man, pray for him. God put Him in his office: it would be wrong for us to oppose God by trying to remove him from it."