I can honestly say that I didn't ever see Deliberate Destruction while on the Belt sorting freight. However, there was a lot of times when folks where just plain overwhelmed and had to just keep moving regardless of the outcome, so stuff took what was coming.
There was also a lot of "stupid" boxes. Like the Caterpillar part that was a single steel pin 6 inches in diameter and 14 inches long weighing 90 lbs packed in a simple cardboard box. The guy grabs the box and lifts is off the belt, the part exits the box between the belt and container and creates mayhem.
Or the complete set of china plates packed in a single box with only a single sheet of newspaper between each plate for 'protection', that was a very memorable noise.
Sometimes folks pack stuff like they just don't give a $hit.
I'll have to second all that!
I've been flying in the FedEx Feeder system for 21 years and I've never seen deliberate trashing of freight, although I've seen a few boxes tossed into the truck or aircraft (against policy!).
Packing is atrocious! I've seen all of the above and many car and machinery parts just come without a box, just a label attached.