This is about the one body. When I was a young Christian, I read verse 14 and it seemed obvious to me what it meant, but I drew entirely the wrong conclusion.
This changes the heart. If my sins are forgiven and I am a Gentile and his sins are forgiven and he is a Jew, if we are both forgiven by Christ and it is by Christ alone that we are saved and we stand, then we realise we are one in Christ and we have a kinship and we are grateful to God that we make no difference any more between us. And, of course, the ceremonial law is finished, so the Jew who was foolishly proud of his keeping the ceremonial law has no longer any cause mistakenly to say, ‘I am a Jew; I have the ceremonial law. This alien Gentile does not have the same privilege. He is of an inferior status; he is like an animal in my estimation.’ Jewish foolishness is destroyed and, of course, both parties are brought into gratitude and love to God.