In "God's Word for Today" Gordon Snider writes:
Peter began by addressing the Christian's attitude toward fellow Christians. He was addressing believers who were living under persecution and the stress that creates in relationships. It is easy to be critical and defensive when you are constantly under attack. Peter urged his readers to resist that temptation. The focus should be on what Christians have in common, and not on their differences (“be . . . of one mind”). Attitudes of sympathy, compassion, and consideration were to be prominent. And if they are, Peter reasoned, it will affect the use of your tongue. Words of blessing will be more common than words of criticism. Your words will bring peace instead of division; healing rather than hurt. Your speech will be marked by transparency rather than deception. Verse 12 suggests clearly that such a person is the one who finds favor in the eyes of God.
Source: Building Christian Relationships: Adult Teacher's Insights, page 65.