Let’s take the experiment one step further.
Set up a few old-fashioned catapults or trebuchets, just out of his visual range, and fill them with a bunch of small rocks. When ever he throws a projectile just launch a retaliatory strike with a catapult-full of rocks and see what happens.
How many times do you have pelt him with a salvo of rocks to deter him from throwing rocks at the visitors?
Just once if you use big enough rocks.
Or do what we did during my first tour in Nam, one round to lighten the load his shoulders are carrying, gut him, fill the cavity with spicy stuff, close the hole and put him over a BBQ. Mmmmmmmm DeeeeLicious!
It didn’t matter if they were youngsters or mean old red ass rock apes. After an hour or so over the BBQ, the steaming inside would penetrate the meat with spicy pepper flavors. It was a great way to end the week.
If the chimp learns not to throw rocks for fear of retaliation, then he’s a lot smarter than the Palis.