Was he doing something he shouldn't have been? Was he talking a little too much about partying and not enough about football? Did he get mad because someone asked him about that picture of him rolling a twenty in a Vegas bathroom.
Nope. It was actually just a real big misunderstanding.
Somehow Nike managed to hire some security personnel that had no idea who one of the most famous (or infamous depending on your perspective) quarterbacks in the land is.
Yep, that's the story.
Either these guys are lying their butts off and did just because or they spend no time online, don't read the paper, ignore the tabloids completely, and are not football fans.
To his credit Manziel did as asked and left the field. He probably thought he was being punked. Little did he know it was just because he isn't that famous--yet.