Why does the Body of Christ have to be raptured before God deals with Israel again?
The Body of Christ must be raptured because it is insulated from God's dealings with Israel, both before and after. The Church has to be off the scene so God can pick up dealing with Israel again, resuming the Old Testament program: the tribulation, the coming Messiah, the King, and the Kingdom.
Les explains that because Israel rejected the Messiah and Peter did not succeed in turning Israel to repentance, God brought up the Apostle Paul and began calling out the Body of Christ, primarily from among the Gentiles. That calling has nothing to do with the Old Testament program or the tribulation, since the tribulation is tied to the Old Testament and primarily for the Jew. Therefore, the Body of Christ is insulated from God's dealings with Israel either before or after, and that is why Les teaches the Rapture. The Body of Christ has to be off the scene before God can pick up dealing with Israel again. Les illustrates this by removing the Church section and backing up to the Old Testament economy: the coming of the Messiah, the tribulation, the King, and the Kingdom. When Israel rejected it, God went to the calling out of the Body of Christ; it has to be raptured, and then He will yet bring in the tribulation to Israel. Romans 11:25 is the triggering mechanism for Christ's coming for the Church, though no time element is given.