In his letter to the Galatians (who were Gentiles), Paul (who was a Jew) states that there is neither Jew nor Gentile. Huh? Of course there are Jews and Gentiles. The Bible talks about them all the time:
It says there were Jews who were slaves to Gentiles, and that their city will be trampled by the Gentiles. Jesus became a servant of the Jews so the Gentiles would praise God with them. The Jews and the Gentiles both conspired against Jesus, who was said to be the glory of the Jews and a light for the Gentiles. The Jews and the Gentiles also both conspired against the followers of Jesus, because Jews and Gentiles alike are under the power of sin.
It says God chose Paul to preach to both Jews and Gentiles, and he will save both Jews and Gentiles. Paul taught that Jews and Gentiles should all live like Gentiles. A lot of the Jews and Gentiles thought Paul’s message was stupid and rejected it. But Paul said all the Jews and Gentiles who believed would be saved. God is the God of both Jews and Gentiles, and he will judge both Jews and Gentiles according to what they do.
So clearly it’s absurd to say Jews and Gentiles don’t exist. Or even that there are no Jews and Gentiles among the Christians. Maybe what Paul meant to say was just that there’s no significant difference between Jews and Gentiles? That’s not what he said in the first verse referenced in this post (though he does say that elsewhere). But even if that’s what he meant, he’s still wrong, according to the Bible.
The Bible says the Gentiles were so impure that the Jews had to keep themselves separate from them. When they intermarried with them, it was a terrible appalling sin. It was against the law to associate with them at all (though Peter claims God changed his mind about that). Jesus told his disciples to preach to the Jews, but to avoid the Gentiles.
Paul tried to preach to the Jews, but they rejected his message, so then he only preached to the Gentiles. But he thought the Jews would eventually accept his message out of envy, after they saw all the Gentiles get saved. And he thought the Gentiles owed the Jews money for the privilege of getting a share of the blessings that were really meant for the Jews.