Here, the knock on the helmet could be charged as 4th degree assault, certainly not justified in a simple trespass case. If I had been called out, the trespassers would each have been given a citation, the property owner would have gotten one for himself. That's what we pay those big bucks to the judges, let them decide which is the greater wrong.
However, if damages were done and could be proven, then it would be criminal trespass, but still wouldn't justify a laying on of the hands, the owner should have backed away and let his tax paid civil servants handle the issue.
I used to have a problem with 4 wheelers running up the river bed and across my property. It is a navigable stream and as such, is open to the public, but once you step onto the bank, you're trespassing. My issue was that they were cutting deep ruts and spinning donuts in a river bottom that is highly erodible since it floods at least twice a year.
Since there were so many people doing it, it seemed to me that the simplest solution was to just fence it off. It does get to be a pain unlocking and locking back a gate that I'd rather not have there in the first place, but at least now I don't have a problem with the 4 wheelers. They still run the river bank on either side of me, but they don't get across my property.