Palpable Disappointment

In Ch 3, it seems as if Paul breaks off from the disappointment of his experiences with the apostles to launch into the Galatians who are in the process of being led astray. But it almost seems as if Paul alone is fighting for truth, battling with Peter and even Jesus' own flesh and blood to defend the centrality of the cross. I wonder whether Paul has worked himself up into a stew with his reminiscences and now is laying into the Galatians or whether he is genuinely trying to reform their faulty thinking with generous rhetoric. Either way, he is taking no prisoners.