Why wasn't God being unfair when He went to Israel instead of the Gentiles first?
God was not unfair because He knew the Gentiles would trample His offer of salvation underfoot for 2,000 years. So He dealt with one nation, Israel, intending to use them to go back to the Gentiles; when even that favored nation failed, He turned to Gentiles with grace.
Les teaches that God was not being unfair because He knew in advance what the Gentiles would do with His offer of salvation: they had trampled it underfoot for 2,000 years already. Therefore God said He would do something different—deal with just one little nation of people, Israel, and bring them to the place where He could use them to go back to those Gentiles. But even the favored nation failed. So God then went to the Gentiles without the nation of Israel. Paul trumpets this: the Jew had the promises, rejected them, and God sent them into dispersion. He turned to the Gentiles with salvation not based on temple worship or keeping the Law, but on the fact that when Christ died, He paid the sin debt. Because Israel was set aside, salvation came to the Gentiles. Yet God is not through with the Jew; He will still come back to the Jew.