Earlier quoted context omitted.
I don't think you understand the threat profile of a large public event. The typical threat to events like this are idiots who mimic crap they see on YouTube. Public safety isn't an exercise in evaluating every theoretical threat, because that list is too long to address with limited resources. It is an exercise in evaluating which threats are most commonly to be exploited, and the easiest to protect against. This is…
Raspberry pis are not a "likely threat," because they are not a threat. It's hard to get away from that fact when evaluating the absurdity of the ban.
Cops are going to turn you away from this event if you carry in something that looks like circuit boards and wires.