To deal with those groups you must establish the scripture as the word of God written and authoritative.
I use the 1689 confession of faith.
Chapter 1: Of the Holy Scriptures
1._____ The Holy Scripture is the only sufficient, certain, and infallible rule of all saving knowledge, faith, and obedience, although the light of nature, and the works of creation and providence do so far manifest the goodness, wisdom, and power of God, as to leave men inexcusable; yet are they not sufficient to give that knowledge of God and his will which is necessary unto salvation. Therefore it pleased the Lord at sundry times and in divers manners to reveal himself, and to declare that his will unto his church; and afterward for the better preserving and propagating of the truth, and for the more sure establishment and comfort of the church against the corruption of the flesh, and the malice of Satan, and of the world, to commit the same wholly unto writing; which maketh the Holy Scriptures to be most necessary, those former ways of God's revealing his will unto his people being now ceased.
(
2 Timothy 3:15-17;
Isaiah 8:20;
Luke 16:29, 31; Ephesians 2:20; Romans 1:19-21; Romans 2:14,15; Psalms 19:1-3; Hebrews 1:1; Proverbs 22:19-21; Romans 15:4; 2 Peter 1:19,20 )
2._____Under the name of Holy Scripture, or the Word of God written, are now contained all the books of the Old and New Testaments, which are these:
OF THE OLD TESTAMENT: Genesis, Exodus, Leviticus, Numbers, Deuteronomy, Joshua, Judges, Ruth, I Samuel, II Samuel, I Kings, II Kings, I Chronicles, II Chronicles, Ezra, Nehemiah, Esther, Job, Psalms, Proverbs, Ecclesiastes, The Song of Solomen, Isaiah, Jeremiah, Lamentations,Ezekiel, Daniel, Hosea, Joel, Amos, Obadiah, Jonah, Micah, Nahum, Habakkuk, Zephaniah, Haggai, Zechariah, Malachi
OF THE NEW TESTAMENT: Matthew, Mark, Luke, John, The Acts of the Apostles, Paul's Epistle to the Romans, I Corinthians, II Corinthians, Galatians, Ephesians, Philippians, Colossians, I Thessalonians, II Thessalonians, I Timothy, II Timothy, To Titus, To Philemon, The Epistle to the Hebrews, Epistle of James, The first and second Epistles of Peter, The first, second, and third Epistles of John, The Epistle of Jude, The Revelation
All of which are given by the inspiration of God, to be the rule of faith and life.
(
2 Timothy 3:16)
3._____ The books commonly called Apocrypha, not being of divine inspiration, are no part of the canon or rule of the Scripture, and, therefore, are of no authority to the church of God, nor to be any otherwise approved or made use of than other human writings.
(
Luke 24:27, 44; Romans 3:2 )
4._____ The authority of the Holy Scripture, for which it ought to be believed, dependeth not upon the testimony of any man or church, but wholly upon God (who is truth itself), the author thereof; therefore it is to be received because it is the Word of God.
(
2 Peter 1:19-21; 2 Timothy 3:16; 2 Thessalonians 2:13; 1 John 5:9 )
Once the word of God is established, then look to show which Jesus is revealed in scripture.;
2cor11:
3 But I fear, lest by any means, as the serpent beguiled Eve through his subtilty, so your minds should be corrupted from the simplicity that is in Christ.
4 For if he that cometh preacheth
another Jesus, whom we have not preached, or if ye receive
another spirit, which ye have not received, or
another gospel, which ye have not accepted, ye might well bear with him.