Honestly, chapters 4-6, of Ephesians should be read together and not in pieces. Ephesians chapters 1-3 are about God’s love. Chapters 4-6 are about loving others and how we should relate to people in a godly way. Unity is a nice thing and Ephesians 4:1-7 addresses unity, but we need to see the rest of Ephesians to see what pitfalls threaten unity and how to deal with them. For example in Ephesians 5:11, God is pretty clear that we can have no fellowship with the unfruitful works of darkness. How does this relate to longsuffering and forebearing (Ephesians 4:2)? We have to read Ephesians 4:23-27 and other sections to read verse 2 of chapter 4 correctly.
23 And be renewed in the spirit of your mind; 24 And that ye put on the new man, which after God is created in righteousness and true holiness. 25 Wherefore putting away lying, speak every man truth with his neighbour: for we are members one of another. 26 Be ye angry, and sin not: let not the sun go down upon your wrath: 27 Neither give place to the devil. (Ephesians 4:23-27)
This is not hard to understand because it is specific. It is much more difficult to just read Ephesians 4:1-7 without the context; one would have to extrapolate one’s own theology on the true meaning of unity. ‘Putting away lying’ is an important concept. Lying can be a tool in manipulation, gossip and very subtle conversational tact. Speaking the truth in love can dispel genuine anger maybe not for every side involved. When one person loves the truth, the sun will not go down on that person’s wrath. It is speaking the truth in love that causes one to peacefully grow up!