What does Peter's hesitation at Cornelius's house show about whether he had understood Paul's gospel of grace?

Les explains that Peter's vision of the sheets and his words at Cornelius's house demonstrate that the Jerusalem Jewish believers were still basically law keepers and had not comprehended Paul's gospel of grace. Peter said, "Not so, Lord," because he had never gone contrary to the law and ate kosher. At Cornelius's threshold, Peter told him it was unlawful for a Jew to keep company with a man of another nation. Les says if Peter understood Paul's gospel of grace, that would not have even crossed his mind; he should have been thrilled to enter the house of a military officer. Instead, it was bugging him because, as a good Jew according to the law, he could not go in. God had made it plain this was what He wanted, but Peter's hesitation showed his law-based mindset. The controversy with Jerusalem emissaries undermining Paul's congregations and questioning his apostleship illustrates the same failure to understand grace.