It seems typical of a JW to look at the passage cited but to nOT read the context or even the chapter that it is located in because if a JW did, they would find this:
12 I am writing to you, little children, because your sins have been forgiven you for His name’s sake.
22 Who is the liar but the one who denies that Jesus is the Christ? This is the antichrist, the one who denies the Father and the Son. 23 Whoever denies the Son does not have the Father; the one who confesses the Son has the Father also. 24 As for you, let that abide in you which you heard from the beginning. If what you heard from the beginning abides in you, you also will abide in the Son and in the Father.
1 My little children, I am writing these things to you so that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous; 2 and He Himself is the propitiation for our sins; and not for ours only, but also for those of the whole world.
7 Beloved, I am not writing a new commandment to you, but an old commandment which you have had from the beginning; the old commandment is the word which you have heard. 8 On the other hand, I am writing a new commandment to you, which is true in Him and in you, because the darkness is passing away and the true Light is already shining. 9 The one who says he is in the Light and yet hates his brother is in the darkness until now. 10 The one who loves his brother abides in the Light and there is no cause for stumbling in him. 11 But the one who hates his brother is in the darkness and walks in the darkness, and does not know where he is going because the darkness has blinded his eyes.