To call the whole "it's ok to be white" thing "code" is a reach. The whole point of it was to call out the hypocrisy and, potentially, racism of anyone who was offended by such a benign statement. That's not code, and it was extremely obvious at the time the intent.
It started as a trolling campaign in 2017 from 4chan's /pol/. It spread outside of 4chan mostly due to David Duke and The Daily Stormer. It might have some history even longer than that because in 2001 it was used as a title track by a white power music group called Aggressive Force and was also found in 2005 fliers by United Klans of America
