I learned something a little more clearly in preparing to answer this thread. The full context of your passage is this:
12 No one has seen God at any time. If we love one another, God abides in us, and His love has been perfected in us. 13 By this we know that we abide in Him, and He in us, because He has given us of His Spirit... 16 God is love, and he who abides in love abides in God, and God in him. 17 Love has been perfected among us in this: that we may have boldness in the day of judgment; because as He is, so are we in this world. 18 There is no fear in love; but perfect love casts out fear, because fear brings torment. He who fears has not been made perfect in love. 19 We love Him because He first loved us. 20 If someone says, “I love God,” and hates his brother, he is a liar; for he who does not love his brother whom he has seen, how can he love God whom he has not seen? 21 And this commandment we have from Him: that he who loves God must love his brother also.
So the teaching is essentially saying this: That we will not come to the place of perfectly loving others at all times unless we eliminate fear from our hearts and minds completely. So long as we walk in any fear whatsoever, to the extent that we do, our own fears of what others might do to us will torment us and we will "feel" the pain of what they might do, even if they never actually do so. We make them to harm us through our own anxiety and imagination, and this causes us to lash out at them instead of love them. In other instances, they truly are sinning against us, yet it is our fear that things will not be set aright that causes us to lash out, taking judgment into our own hands rather than letting judgment be God's.
And here's an interesting observation: The apostle Paul even struggled with this. It's why he could come off a pretty rough and aggressive sometimes. In one place, while listing the things he suffered in preaching the gospel, he said the following:
23 Are they ministers of Christ? (I speak as a fool) I am more; in labours more abundant, in stripes above measure, in prisons more frequent, in deaths oft. 24 Of the Jews five times received I forty stripes save one. 25 Three times was I beaten with rods, once was I stoned, three times I suffered shipwreck, a night and a day I have been in the deep; 26 In journeyings often, in perils of waters, in perils of robbers, in perils by mine own countrymen, in perils by the heathen, in perils in the city, in perils in the wilderness, in perils in the sea, in perils among false brethren; 27 In weariness and painfulness, in watchings often, in hunger and thirst, in fastings often, in cold and nakedness. 28 Beside those things that are without, that which comes upon me daily, the anxiety over all the churches. (2 Corinthians 11)
Paul had reason to be anxious for the churches. Satan was constantly coming in behind him and spreading heresy through the congregations he was ministering to, which is why so many times he wrote, "I do not want you to be ignorant of how many times I wanted to come to you, but the enemy hindered me."
This is where I struggle as well. I know how good the enemy is at deceiving, which brings me into anxiety. When attacked on a position I know to be the truth, I usually have no real concern about how people see me for my own sake (I honesty don't care), but I have a great deal of concern for how the truth will appear in the eyes of others if such attacks are not addressed, and firmly, and if I fear the truth appears as if it is being cast down, I can retaliate, and rather viciously sometimes.
Still working through that one, but I find it interesting that even the strongest in the Christian faith struggled with casting out all fear to walk in perfect love towards others at all times. I think it involves trusting in God that even if your work can seem to get torn down (for a time, or even permanently in some instances), God has all things in His hands, and it will not be your fault if some people go to Hell because you were not there to save them.
Any thoughts?