Paul accurately records that the Israelites had a zeal, "but not according to knowledge." They were confused. The apostle Paul before his conversion is probably the prime example of such misdirected zeal. What did his zeal do to him? It so preoccupied his mind that it forced him to perceive Christ and Christians as enemies of the faith of his fathers. He was responsible for throwing many of them into prison, and some were even put to death as a result of his zeal. His mind could not tolerate anybody who thought a little bit differently from the way he did. God had to strike him down on the road to Damascus.
Even today, the Israelitish nations are dotted with church buildings, and the vast majority of the people are truly sincere, even zealous. However, true knowledge is still lacking. However, there is a difference between the Israelitish zeal of today and the zeal of Paul's time. The zeal in Paul's time reflects the Jewish belief that a person is capable of justifying himself before God on the basis of merit. In other words, as long as a person did what was considered "good works," he was earning "points," and God was obligated to mark this to his account and, therefore, owed him something.
Today's Israelites have gone all the way to the other end of the pendulum's swing, largely having thrown out responsibility to law and substituted a specious faith. Justification is by grace through faith (Ephesians 2:8), but that faith includes obedience to law, as Paul clearly shows (Romans 2:13; 7:7-12). If the law has been done away, then there is no such thing as sin—but sin certainly exists! James explains that the faith that is "living" obeys the royal law (James 2:8-12, 18-26). Thus, the faith that justifies—or is the basis by which God will justify—is an obedient faith. Most of Protestantism does not believe that way, holding to a "just-as-I-am" faith.