Hmmm. HAL Pilot might have the explanation. It defintiely wasn't a religious thing, just two strips of black masking tape stuck diagonally across the top of his cadet cap. This guys certainly wasn't the football carrier. Just some chap in the crowd.
It looked for all the world like a protest but I assume that his CO would swallow his tongue if one of his charges started pulling peacenik demos at graduation. If there was something similar at Normandy, maybe it's a remembrance thing, similar to wearing a black armband? I'm still surprised that such personal expression would be allowed.