Bible says in Proverbs 28:13 He that covereth his sins shall not prosper: but whoso confesseth and forsaketh them shall have mercy.
Dear brother, according to this word when you confess and leave it God is gracious enough to forgive you and any addiction is sin and The good news is the Lord JESUS CHRIST will give total and complete victory over addictions. For the Christ-follower the testimony is not, I'm a recovering addict but rather JESUS CHRIST HAS SET ME ABSOLUTELY FREE OF ADDICTIONS, but it is free will. You personally must make a serious commitment to be free. As you said that brother is not a christian, how will he know unless you tell him about this. So make an attempt to tell him how demonic it is, because the bible says Those who attempt to turn anyone away from the Lord (Deut. 13:6-9) is a curse. He needs JESUS first then deliverance follows because Romans 10:17 says So then faith cometh by hearing, and hearing by the word of God. JESUS is the Only Deliverer.
Lord i Pray that You will give wisdom and words to this brothter tell about the love of Christ to his friend John and help him to come out of it. In JESUS delivering name i pray. Amen. Dont waste time. His soul should not perish.