One time I had, in a cat carrier, a cat. I hardly remember the circumstances, but I remember that the cat was all jiggled up from having been transported, and was anxious and fearful, and I arrived at my ex's place with this cage full of cat, and put it down. I opened the door to the cage, and the cat didn't come out.
So, my ex stuck his arm in to try to get hold of the cat, and get it out.
He did this before I realized he was going to, else I would have stopped him. Anyone who puts his arm into an enclosed space with a frightened animal is going to get hurt. And he did. And he slammed around in fury and demanded the cat be punished.
I could understand his instant rage, because he was injured. But I could more closely understand the cat's reaction, because of the cat's circumstances.
Yes, it was a well-known human reaching in. Yes, it was a safe environment. But the cat was fearful, and it lashed out.
And the human was in pain, and he lashed out.
They eventually got over it. And the human learned to relax and not try to force a cat out of a cage. And the cat eventually relaxed and learned not to fear transport so much.