Why would the Pharisees have wanted to kill Jesus after hearing 'there is none righteous, no not one'?
They wanted to put him to death because the declaration “there is none righteous, no, not one” struck at their self-righteousness. They viewed themselves as righteous, especially the most religious Jew, so being told that no one—Jew or Gentile—is righteous exposed their sin and destroyed their claim to special covenant standing.
Les explains that the Pharisees were righteous in their own eyes, so the statement that no one is righteous—not even the most religious Jew—was a direct assault on their identity. For nearly 2000 years, Israel had been taught they were special, a covenant people set apart from the rest of the world, not to intermarry and to stay within their tribes. The idea that Gentiles were just as good as Jews sent the Jewish community into orbit. Les notes that this was the crowning reason: the Apostle’s message that there is no difference between Jew and Gentile infuriated them. They followed him from city to city, trying to defeat him, and plagued him until his death. So when they heard “there is none righteous, no not one,” they could have put him to death, because it made plain that no one is righteous, not even the most religious Jew.