Uncle Pug:
It is a big fish with a nasty attitude. They will attack if you swim too close to them. Sometimes they get angry for no apparent reason. <snip>
What is and isn't harassment should perhaps be left to the animal to decide and act on by fleeing, biting, or approaching for a look-see. I feel that we divers should let the animal make the first move, and then we should just take the hint, whatever it appears to be.
I don't recall ever seeing a cabezon, but we have a fish with a similar bad attitude here in SEA. The titan triggerfish charges mainly during nesting season (when they can be seen hovering head down over the sandy patch where they have eggs). These guys are big and brutal. They can bite sizeable chunks out of arms and legs, and even out of rubber fins. Most dive briefings in areas they populate warn about staying clear of them and swimming away from their territory when they are spotted guarding their nests. (I doubt one would tolerate two divers corraling it to take pictures, even when it wasn't nesting, so its definition of harassment is quite broad, I guess.)
On one memorable dive, I recall an Italian gent purposely invading a titan triggerfish's nesting area with a videocam to film it as it vigorously defended its territory. The diver eventually "had to" strike out at the fish with the camera to avoid getting bitten. More power to the fish!
When I'm underwater, I'm acutely aware that I'm an alien in a habitat not meant for my species. If any particular marine creature suffers threats from other inhabitants of the realm, even to the extent of losing its life, that's only to be expected. IMO, what is to be avoided is that they should suffer intentional harassment from me, an outsider. (And, no, I don't eat them.)