Meekly but firmly with the Bible [2Tim 2:25-26].
You never know, when you first start to point out a scriptural problem, whether the individual is going to receive the correction or not. To us, it is helpful to mention that his beliefs are unscriptural and to ask if we might show him from the Bible the scriptural truth.
If he agrees, then we open the Bible and let him read for himself, giving him plenty of time to “digest” the passage, to ask questions for clarification and to comment if need be. If he understands and receives the verse or passage, then we’ll take him to another verse or passage to further help him “see” the truth [in the mouth of two or three witnesses every word may be established, Matt 18:16].
We don’t usually overwhelm a person with the truth if he is receiving it, unless he really wants more. We’ll let him have some space and time to think it over. We’ll get together another time and go over more scripture when he is ready.
If the fellow is a heretic and he simply wants to argue positions, we’ll follow Titus 3:10. We have no problem letting a fellow go on in his ignorance if he doesn’t want the truth from God’s words [1 Cor 14:38].
Hope this helps,
Pastor Bevans Welder