The idea is beyond absurd, but to be completely honest, living on the other side of the ocean makes me seem absurd the whole idea of people being able to even carry their guns to a stadium, if only to check it in.
Not trying to start a pro or against guns issue since it's a complex topic, but allow me to get where I want to with an example. Now, I honestly don't know how widespread is the ban of smoking in public places, but I'm old enough to have lived in the times where you could smoke in bars and pubs, I remember going to a metal pub and coming home with the clothes stinking. Then in 2002 I believe the ban was applied, and smokers simply went outside to smoke.
Now, if such a ban was never applied, us non smokers would simply go along with it and reason along the way of "Mh, I'm going to the pub tonight, better wear clothes I'll wash tomorrow since they'll be stinking anyway". Just as you're debating about the reasonable way to handle guns at sport events (as someone suggested, just check them in and pick them up when you go away, for example).
But the point is, you're debating about the possible places where it's acceptable to bring a gun because that's your reality. Just know that there's another reality where not having a gun works perfectly fine. I know the world is not the same everywhere and what may works in some nations or continents, may not work in another, but I'm happy and consider myself lucky to live in a place where having to have a gun even in a parking lot of a stadium is not a legitimate and appropriate concern.