The gospel requires a response.
If you are a Christian and you are AVOIDING church membership then you are LIKELY living in sin.
Paul is teaching that no true believer will be removed from the tree, but false believers who arrogantly presume that their own "righteousness" will lead to God's kindness will be removed. This is done so that everyone will know that salvation is a merciful gift that they do not deserve.
God has a glorious plan for the salvation of His people.
Paul’s evangelistic passion (also) flows out of his theological conviction that men are both rebellious and responsible.
Paul’s evangelistic passion flows out of his theological conviction that God is both faithful and free.
God mercifully loves Jacob in spite of his wickedness, and God justly hates hates Esau due to his wickedness.