In one of my courses I learned a principle of interpretation called the "No Fishing" rule. If you were to go somewhere near a body of water and see a sign that read NO FISHING, what inference could you draw about the purposes and origins of the sign? You could prima facie observe that some persons had been fishing there when they weren't supposed to; or at least you might infer that there was a risk that persons fish there when they are not supposed to. This principle also works in interpreting scripture: the moral injunctions and proscriptions an author includes in his work might tell us something about the context and situation of his target audience.
One of the topics that comes up again and again in 1 John is that of love. More than anything else John insists that that the members of his audience love one and other, insisting even that this would constitute a definitive evidence of their having met God (or not): Whoever does not love does not know God, for God is love (1 John 4.8). In light of the No Fishing rule, therefore, we can infer that the congregation to which John had written was seriously struggling in this regard. They had to be told again and again that God has shown love for them, that Christ has laid down his life for them out of love, and that therefore they were expected to live in the same intense love (3.16).
The thought that John's audience was experiencing considerable agapic deficiencies is plausible enough in light of the evidence of the letter itself. It never occurred to me, however, that his audience might have been experiencing such tremendous difficulties. I suppose the reason is that 1 John reads as a very "gentle" and "soft" text. It doesn't have the fire and brimstone of 1 Corinthians, for instance, where the nature of the text as rebuke is evident.
I appreciate that about John: not only does he call for his audience live in love, but he demonstrates a certain gentleness of character even in the rebuke. 1 John doesn't read like a "hard" text. To my mind it has a "soft" character, and I think it is only fitting that it do so, because the love of God as demonstrated in Christ Jesus is a soft love. It is God's Son dying for the sins of humanity and giving life to the dead (4.9-10). It's a love that takes harm upon itself rather than issuing harm on the beloved (tough love). The tone of John's epistle fits well with this.
I think I would do well to learn from John's rebuke in this letter. Oftentimes I am tempted to come off as a strict moralist, laying down a law with harshness. John's method, however, is to remind others of the love of Jesus Christ and God the Father as demonstrated by what they've done for us: dying for our sins and giving us eternal life (5.11). That is, after all, how you inspire love in another person: through showing your own goodwill and winning them over with goodness. I think that is how you inspire love in your audiences as well: you warm them up to God and to each other through a reminder of God's goodness towards them.