<font color=blue>"If they hit you, it's because they're trying to hit you."</font color=blue>
I seriously doubt that any golfers were trying to hit Jon. If these guys (a.k.a. duffers) are hitting balls over on to Jon's property, it's a sure bet that they've lost a bunch of other balls during their round of "hacking". They're not going to want to be whacking balls off the course 'cause they can't afford to replace them all.
<font color=blue>"If it happens, perhaps the golf course owners would pay for the repairs."</font color=blue>
Unfortunately, this probably will never happen since in most states, providers of recreational activities are generally protected by recreational immunity laws. In other words, the golf course can't be held responsible for what a golfer does. Another consideration is which came first, Jon's house and property or the golf course? If the golf course was there first, and Jon knew it was there when he bought the property, I don't think Jon would have much to stand on if he wanted to file a suit.
Best suggestion might be to plant a row of fast growing trees to act as a buffer and screen.