I think it's easy to under-estimate the ignorance of people who don't go to football very often when it comes to the rules. I've taken people a couple of times who have been really surprised that they couldn't take drinks to their seats. Someone going along for the first could easily just wander...
Seems ridiculously harsh to me. Just take it off him.
At the women's game last week a steward said to my wife "Sorry but you can't bring that up here- no alcohol allowed in the seats" as she tried to walk up the steps with a large glass of white wine. She replied "It's not alcohol it's apple...