What is their rationale?   
→ doctrinal error
→ wrong baptism
→ church affiliation
→ appearance
→ language
→ associations
→ Jewish feasts
→ Greek and Hebrew

Elitist Christians are the equivalent of the Pharisees of Jesus day.   Such do not distinguish between the gift of God, Eternal Life, and Soul Salvation.   
Furthermore, they fail to understand that the seed is the Word Of God, the Holy Spirit is the life producer and their only contribution is the Good Ground of Faith.   

For it is God which works in you both to will and to do of his good pleasure. - Phi 2:13 To the extent that you work out your Soul Salvation you will see the Holy Spirit perform godly acts through your life.

The main reason Elitist Christians exist is the subtlety of Satan who plays on the pride of life.   

For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world. - 1Jn 2:16 We are Spiritual Minded and no longer Carnal Minded.

The reality of the laws of the Kingdom of Jesus Christ is that Abundant Life is the blessing of obedience while the 'curse' of disobedience is the lack of Abundant Life.   

At the Judgment Seat Of Christ the obedient will receive rewards while the disobedient will be saved as by fire receiving no rewards.   

For by grace are you saved through faith; and that not of yourselves: it is the gift of God: - Eph 2:8 We are saved because God willed it (Heb 8:12) and made it possible and legal through the shed blood of Jesus Christ (Heb 10:10.) Salvation is totally an act of God's unmerited favor - Grace.     Our part is to have Faith in His Word - the Written Word and the Incarnate Word (Act 16:31.) We have all been given The Measure Of Faith (Rom 12:3.) It is that gift of Faith than enables us to believe on the Lord Jesus Christ through whom we receive Grace (2Pe 1:3.) Once we believe on the Lord Jesus Christ, the Faith Of Christ provides all the benefits of Grace (Rom 5:2.) The Faith Of Christ is the foundation of Grace (Rom 5:19.) We are not supposed to trust in our Faith but, rather, trust in the Faith Of Christ (Phi 2:8-11.)

And they said, Believe on the Lord Jesus Christ, and you shall be saved, and your house. - Act 16:31 We connect The Measure Of Faith that God gave us at birth with the Gospel of Jesus Christ and we are Born of the Holy Spirit and become Sons Of God.

That if you shall confess with your mouth the Lord Jesus, and shall believe in your heart that God has raised him from the dead, you shall be saved. - Rom 10:9 This is the encapsulation of Grace, clearly pointing out our part which is Faith in Jesus and confession of Him as risen Lord and Saviour.      The implication of our part being to believe on Jesus Christ and confess Him as risen Lord, is that He has done everything else!      It is why we call it amazing Grace!      It is why the Gospel is nearly too good to be true!

For with the heart man believes unto righteousness; and with the mouth confession is made unto salvation. - Rom 10:10 It is Heart Faith that enables the miracle of the New Birth.

For we must all appear before the judgment seat of Christ; that every one may receive the things done in his body, according to that he has done, whether it be good or bad. - 2Co 5:10 The Judgment Seat Of Christ is the place where we come to understand and give account for that which we did in the name of Christ Jesus.     Some of it is good and some of it is bad.      This is kind of like a debriefing so that we understand more perfectly who Christ is and what the Gospel entails.      It is a fact that some believers will have been so messed up in their theology that they are saved as by fire - have no good works to show (1Co 3:15.)

If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire. - 1Co 3:15