You can't have love without the truth. Love is the truth. Love is walking in the truth toward God and other people. It is fulfilling God's law toward God and other people. God couldn't love us if He was contaminated by falsehood or error. You can't bear someone else's burden before you bear your own. Before you restore, you consider yourself. When you consider yourself, you aren't comparing yourself to others, but to the truth.
Since love wasn't happening without the truth, the truth was priority. That meant you couldn't show acceptance to whom? As people look at John's example in 2 John, I've noticed that they get very specific at where the lines are drawn. Is that what John meant for us to do, when we look at all of 2 John and 2 John in the context of Johanine writings?
When you read the first six verses of 2 John, it's about the truth. We should assume all the truth, especially when we read what Jesus taught John in John 14-17. Jesus said all His words, commandments, and sayings. When Jesus said we were sanctified by the truth, was it just the truth about His nature, that He was God come in the flesh? No. That's also contradictory to many other passages on separation and unity.
Is it only very specific truths that form a boundary line for the limitations John bring in 2 John 7-11? Here are those verses:
7 For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist. 8 Look to yourselves, that we lose not those things which we have wrought, but that we receive a full reward. 9 Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son. 10 If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed: 11 For he that biddeth him God speed is partaker of his evil deeds.
John rejoiced that the household to which he wrote was walking in the truth, which was walking in the Lord's commandments. That was love. He didn't want that to change because of the influence of teachers they would welcome without limitation. John wanted limitation.
The world of the apostle John, the Hellenized and Roman world, affected by Babylonian mysticism, denied certain teachings that clashed with its views, positions that contradicted the truth. Docetism was a unique problem that the elder lady and her children were facing. John gives this specific example. Is it a case study or comprehensive? Is it only docetists or a little broader, people proclaiming a wrong Christology, that would set in motion the actions that John prescribes in 2 John 10-11? Do churches receive not only and bid not Godspeed only those who are messed up in a very narrow category of false doctrine, or is it those who deny any biblical truth, this one just the one he highlighted as a contemporary concern?
John wanted those children walking in the truth. Anyone who comes along and tells lies he didn't want to abide. I'm saying he's giving a specific example of false teaching, not limiting to that. If we were being limited only to shunning docetism, we have many other New Testament texts that mention many other falsehoods from which to separate.
It's clear false doctrine about Christ should set in motion the shunning of 2 John 10-11. However, anyone who allows for any error becomes a partaker in that error when he will not separate over it. The principle works the same. Read verse 11. It's axiomatic. You are a partaker of the false teaching, whatever it is, when it is false, not just false doctrine about Christ.
Almost all evangelicals don't even practice the specific case study of 2 John 7-11, let alone the overall teaching about treatment of doctrinal and practical errors or lies. Fundamentalists are being very narrow now too about what they might separate over, if anything. I don't believe that was John's point though. He wanted all the truth protected and the people protected, whom error would harm.
All lies, all falsehoods harm. They are contradictory to God, Who is Truth. John was providing a case study for what to do when lies came along. Truth trumped hospitality. When Paul said in 1 Timothy 1:3 to "teach no other doctrine," he wasn't being selective and ranking doctrines. He said "no other doctrine." No false doctrine should be allowed in a church. Specific false doctrine about Christ was merely a case study, not comprehensive, that is, the only doctrine to merit the treatment that John prescribes.