The school handled it badly. They have no right to deprive him of a diploma he earned and at any point prior to walking on stage, they could have taken him aside, and explained the policy issue in stead of waiting until he is up there to humiliate him. That's just wrong.
DECADES ago, when I graduated, the schools were already really cracking down on graduation antics. We were all warned that any theatrics would likely get our diploma withheld.
Considering the increased SJW shit AND the lure of posting videos for internet likes, I can only imagine the difficulty that schools face trying to keep control during these events.
This guy choose to make a political statement.
Maybe we just need to admit that due to increased diversity and polarization, we are no longer a society that can have nice things, like graduation ceremonies.