What did Les teach about religion and attempts to kill Paul?

Religion, especially Judaism, can quickly produce murderous attitudes toward anyone who opposes it. When Saul disputed boldly with the Grecians—non-Palestine Jews—in Jerusalem, they could not tolerate opposition to Judaism and sought to kill him. Killing the opposition was their preferred way to eliminate it.

Les teaches that there is nothing that preempts murderous attitudes faster than religion. In Jerusalem, Saul spoke boldly in the name of the Lord Jesus and disputed against the Grecians, who were non-Palestine Jews, not Gentiles. Because they could not stand anyone doing anything against Judaism, they went about to kill him. Les explains that if they had opposition to Judaism, the best way to get rid of the opposition was to kill them, and that is what they attempted to do with Saul.

Acts 9:29

And he spake boldly in the name of the Lord Jesus, and disputed against the Grecians: but they went about to slay him.

Why did the Grecians try to kill Paul?

The Grecians, defined here as non-Palestine Jews who were citizens of other nations, tried to kill Paul because he disputed boldly against them in the name of the Lord Jesus. They could not tolerate opposition to Judaism, and their murderous attitude led them to attempt to kill him.