Why would Christianity not have survived without Peter's defense that Gentiles could be saved apart from the law of Moses?

Les explains that the Judaizers had been pressing Paul, insisting his gospel was not sufficient unless Gentiles also became keepers of the law and practitioners of circumcision. Finally, Peter wakes up and comes to Paul's defense. Les says that had Peter not done so, Paul's gospel, and Christianity as we know it, would have died right then and there. Though God is sovereign and could have done something else, in the unfolding account, unless Peter defended the fact that Gentiles could be saved without coming under the law of Moses, Christianity would never have survived. Peter then asks why they should test God by putting a yoke upon the neck of the disciples—a yoke neither the fathers nor the apostles had to chafe under, because the law was severe if they were really going to keep it.