Okay. Imagine if the Giants fan had been able to defend himself.
Have you ever been in a situation in which you had to brandish a firearm at someone? Both times I have had to do so, there was no “blazing away” necessary. My attacker(s) took one look at the gun and fled.
There are already laws against being “hopped up” while in possession of a firearm.
Finally, laws are for the law abiding. A criminal who wants to use a firearm for evil purposes at a sporting event is going to use a firearm for evil purposes at said sporting event. Allowing law abiding people to arm themselves for self defense is never a bad idea, in my opinion.
You have a mob scene leaving a sports venue. Think about several fans going off on opposing rival fans.