I mention all this because Nick Duke has a nuanced, careful and—yes, it has to be said—polite (It's a good 'polite' though) three part discussion of the misleading rule of thumb ‘In Essentials Unity, In Non-Essentials Liberty, In All Things Charity’ (where he argues among other things that this lovely-sounding expression is both too broad and too bland). In his discussion of 'speaking the truth in love', (in part III), he has this to say:
This is a refusal to let divisions be final; to be optimistic about change because of the direction of history. Words of truth are the God-ordained way that Christ will build his church (Ephesians 4:11-16) and are the direct expression of his rule in this world. Of course, it will be prayerful speech, for we know it is the Spirit of God that makes the externally clear Word of God, internally clear to the hearer. They will also be loving words for we are speaking to someone for whom Christ died. Yet failure to speak is not an option—for the church is ‘the pillar and buttress of truth’ (1 Timothy 3:15).
Speaking truth in love may take a range of forms: from the confrontation in Antioch (Galatians 2:11) to the tender fatherly words to a church (2 Thessalonians 2:10-12). Both are truth in love and we must not allow love to be defined in such a way as to exclude ‘tough love’. Saying ‘Peace, Peace’ when there is no peace is profoundly unloving. Therefore, when using the categories above, we recognise teaching that will undermine the gospel, we must speak out.
We model ourselves on Jesus who weeps over Jerusalem (Luke 19:41) and desires to gather them as chicks (Matthew 23:37-39), yet in the same breath condemns the teachers of Israel as hypocrites, blind guides, fools and snakes. ‘How will you escape being condemned to hell?’ (Matthew 23:33). If we follow his example, we too will follow the path of the cross.
That last paragraph is a sharp and pointy reminder that loving words will not always be pleasant words, particularly where rank disobedience to the Lord Jesus is involved. Sharp and pointy also, because to use words as Jesus used in pressing the claims of truth is to invite the same fate. Not for nothing does he urge the taking up of our cross as his disciples.
Read the whole thing if you can. Part I is found here and includes an outline and a synopsis.