Paul's Imaginary Rebuttal of the Gentiles in Romans 19

Paul is trying to speak to his Jewish listeners and tell them that God always has been in the business of showering mercy and grace on people who don't belong. Paul tells his projected audience to remember their place. This inclusion of the Gentiles into the fullness of God's story and family is far from unfair. It's the very nature of who God is and who he always has been.