I have always had trouble with the extreme positions of the letters of John (anyone who sins is not from God, etc.). This commentary helped me see the balance and answered some of my questions. Particularly I will take away a deeper sense of the seriousness of sin (I read the beginning of this commentary at the same time as Don Everts book "The Smell of Sin" which was really helpful in further illuminating the severity of sin) and a glimpse at understanding the balance between truth and love.
"If, then, the whole purpose of Christ's first appearing was to remove sins and to undo the works of the devil, Christians must not compromise with either sin or the devil, or they will find themselves fighting against Christ. If the first step to holiness is to recognize the sinfulness of sin, both in its essence as lawlessness and in its diabolical origin, the second step is to see its absolute incompatibility with Christ in his sinless person and saving work. The more clearly we grasp these facts, the more incongruous will sin appear and the more determined we shall be to be rid of it." (pg. 129)
"The fellowship of the local church is created by truth and exhibited by love. Each qualifies the other. On the one hand, our love is not to be so blind as to ignore the views and conduct of others. Truth should make our love discriminating. ...Our love for others is not to undermine our loyalty to the truth. On the other hand, we must never champion the truth in a harsh or bitter spirit. Those who are 'walking in the truth' (4) need to be exhorted to 'love one another' (5). So the Christian fellowship should be marked equally by love and truth, and we are to avoid extremism which pursues either at the expense of the other. Our love grows soft if it is not strengthened by truth, and our truth hard if it is not softened by love. Scripture commands is both to love each other in truth and to hold the truth in love." (pg. 207)