There is an attitude that is easy to fall into, one that leads us to think of ourselves in some way as Sky Gods in our Chariots. Just let something happen, though, as here, and we come back down to earth with a thump!
When we are out there doing our aerial stuff we are usually in a very controlled environment with trained professionals around us. Everyone on a ramp has usually had basic safety training so that they know not to stick their heads into a prop or rotor, for instance, when the risks are not as obvious as falling under a vehicle. That said, how often do people fall under vehicles?
Every so often we find ourselves confronted with someone who probably has no business being out there on the ramp. I always take that as my cue to shut down as the first order of business. (Here I am writing as a fixed-wing pilot but I do know my way around helicopters in a very basic way.) That means that I have removed most of the risk from the situation.
From a selfish, self-interested point of view that risk is to my machine and to my licence. A prop strike is going to ruin the machinery and leave me forced to try and escape the stigma and trauma of having injured or killed someone.
There's a far higher risk to the person out there on the ramp, of course. People end up maimed or dead and often very suddenly, when it is then too late to do anything. You may only have seconds to react, when you need to be thinking about protecting the life of that idiot out there wandering around someplace he may have no business being. You are not set there in that cockpit to teach him the hard way the rules for being on a ramp, say.
Citing some rule against "illegal interference" as justifying having an incident might really mean sitting down and having a "reality check."
Aviation is just part of life and not the highest part, so that we have to subordinate it to the higher goal of preserving life. Otherwise you may find yourself in court having this explained to you by the judge or at least having someone from the CAA teach you the error of your ways by grounding you for a while or even forever. Shutting down must be the preferred option whenever there is any doubt, I think.