Well, I'm not sure what kind of events you typically work, but that is in no way surprising to me that rented security was not well-read into who the specific allowed photographers were and weren't.
I guess I just don't understand why it's so apparently offensive to you. The guard simply was not aware that you were authorized. You informed him of the former and that was that. He left you alone once he was made aware. Maybe I'm missing some undertones or implications.
Like I said, I get approached all the time by various parents, coaches, staff, you name it at large competitions with multiple teams like this as everyone is trying to regulate things as best as possible. You just simply inform them that you're authorized and be prepared to provide proof or a PoC they can speak with to corroborate your story. And, that's that. I see this as a success story, that you had to do nothing further once you informed the guard of your authorization and your shooting was in no way further hindered. The guard could have easily continued to badger you or force you to take further time away from shooting.
Just MHO, though, based on my experiences.
Agreed. Were you wearing credentials? If not, he asked, you informed and he moved on. Where's the news story? This is pretty standard.