For me, this often comes in the form of questioning motives. "The Pope said that because..." or "Cardinal so-and-so said that because he secretly hates the church." That's imparting an impious motive. The better response is to assume a pious motive, unless given good and substantial evidence to the contrary, and simply say, "I disagree with him because..." or "He is wrong because..."
Earlier this week, after the leak of Laudato Si, one traditional writer I read criticized the Holy Father (before having admittedly read it, and admitting that the document was unofficial) and said something along the lines of that he doesn't understand what it means to be pope or write an encyclical.
It is acceptable, at times, to criticize even popes and bishops. It is not OK to insult them, and when we insult them privately, that is known as backbiting. In America we often think public officials are fair game, and indeed, political ads and talk shows are full of backbiting. But God's word tell us otherwise. Solomon writes, "Detract not the king, no not in thy thought; and speak not evil of the rich man in thy private chamber: because even the birds of the air will carry thy voice, and he that hath wings will tell what thou hast said." (Ecclesiastes 10:20)