Jesus changes our view of God, he always has. And when Jesus changes our view of God, we will have to answer for these changes because we will find ourselves in places where religious people believe that we ought not to be. Peter understood that following Jesus into fellowship with the Gentiles meant breaking the religious laws of Gods people, and yet he knew he had to move forward.
The most stunning thing about this entire episode is Peters response, and how the it was received. He was sincere, he was known by his accusers, and he was loved by them because he was already in a loving and caring relationship with them. Therefore, he needed only to tell his story and it was accepted. He didn't need to use theological arguments, he didn't need to use the words of the prophets and the law, he simply needed to say 'here is what happened, and this is how it changed me.'
Growth happens best, not in debate with those on the other side of an issue, but rather by remaining in relationship with them.