When he saw many of the Pharisees and Sadducees coming to where he was baptizing, he said to them: “You brood of vipers! Who warned you to flee from the coming wrath?”
–John the Baptist in Matthew 3:7 (NIV)–

You stiff-necked people! 
Your hearts and ears are still uncircumcised.
You are just like your ancestors:
You always resist the Holy Spirit!
–Stephen in Acts 7:51 (NIV)–

May your money perish with you,
because you thought you could
buy the gift of God with money!
–Peter in Acts 8:20 (NIV)–

You are a child of the devil 
and an enemy of everything that is right!
–Paul in Acts 13:10 (NIV)–

Because you are lukewarm,
and neither cold nor hot,
I will vomit you out of My mouth!
–Jesus Christ in Revelation 3:16 (NKJV)–

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There is anger which is not sinful; for anger is found in God himself, in Jesus Christ, in the holy angels, and in God’s people; and a man may be said to be angry and not sin, when his anger arises from a true zeal for God…when a man is displeased with…all false doctrine.
–John Gill–

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Dr. John R. Rice, Why Preach Against Sin? (Sword of the Lord Publishers, 1985).

—. The Soul-Winner’s Fire (Moody Press, 1941).

Leonard Ravenhill, “Be Ye Angry And Sin Not” (Last Days Ministries, 1985).

—. Revival Praying (Bethany House, 1962), ch. 14: “Be Ye Angry.”

John Gill, Commentary on Ephesians 4:26: “Be ye angry, and sin not.” There is anger which is not sinful; for anger is found in God himself, in Jesus Christ, in the holy angels, and in God’s people; and a man may be said to be angry and not sin, when his anger arises from a true zeal for God and religion; when it is kindled not against persons, but sins; when a man is displeased with his own sins, and with the sins of others: with vice and immorality of every kind; with idolatry and idolatrous worship, and with all false doctrine; and also when it is carried on to answer good ends, as the good of those with whom we are angry, the glory of God, and the promoting of the interest of Christ: and there is an anger which is sinful; as when it is without a cause; when it exceeds due bounds; when it is not directed to a good end; when it is productive of bad effects, either in words or actions; and when it is soon raised, or long continues: the Jews have a like distinction of anger.

Adam Clarke, Commentary on Ephesians 4:26: “Be ye angry, and sin not.” We can never suppose that the apostle delivers this as a precept, if we take the words as they stand in our version. Perhaps the sense is, Take heed that ye be not angry, lest ye sin; for it would be very difficult, even for an apostle himself, to be angry and not sin. If we consider anger as implying displeasure simply, then there are a multitude of cases in which a man may be innocently, yea, laudably angry; for he should be displeased with every thing which is not for the glory of God, and the good of mankind. But, in any other sense, I do not see how the words can be safely taken.