I already posted my personal feelings about being insulted throughout my career, and how this wouldn't have phased me, but I'll add a little perspective to it as well.
If you're willing to think that the pizza place kept the original box, for 11 days, then you should also be willing to entertain the idea that the box shown isn't what was pictured initially.
Cops are human, people, just like everyone else. Sometimes there is a breaking point for emotions when you've had a really hard day. Some people react differently.
Imagine not being able to revive the little girl that was found drowning, while the person who called stood on the bank of the narrow river and waited for you to arrive in your squad card. Then picking up something to eat, and your food throw at you. Someone calling you "pig mother fucker" to your face when you were holding their 85 year old mother in your arms while she took her last breath because her grandson thought the house smelled to bad to go in to check on her.
It can get to people. Those two things I posted happened. Did that officer act unprofessionally? Hell no. It wasn't written in the report, or told to his supervisors or other officers. He talked to his wife about it and cried about the things he had to see those days. That doesn't mean it can't get to someone. We aren't super human.