Depends on the nature of the grip.
He could be trying to protect his junk from the leopards, or taunting the leopards by jerking at them. So many options. The past was just as juvenile and perverse as modernity.
This is most likely the explanation. Apex predators will often try to kill the seed of an enemy by tearing off their junk. It's much less dangerous than trying to kill the enemy, and it serves the same purpose of ending their genetic line.
Given that they went to considerable effort to carve it in stone as part of a temple complex, it was likely neither juvenile nor perverse