I’m in the camp of brush cutting is normal activity and no, I would not expect them to stop their maintenance for my reactive, hot, young horse. It might interrupt my plans but at the same time the world does not revolve around me and what I want. (But it should, I say!) So I would take my grumpy thoughts and move somewhere else such as the round pen or another arena. If they stopped their maintenance for you then they’d have to do it for everyone. Foll stop, “No!”.
Standard stable equipment is absolutely something horses need to get used to. Unless a metal rake is tines up in the pathway, then handler needs to hold it together. None of these things should be an issue even if placed right next to a doorway. Horsie freaking out at the four wheeler? Ask for help desenstizing to it. Have horsie chase down treats off the back of it. It really sounds as if the horse AND rider in the scenario need a lot of work on reducing anxiety. They need to work on their own emotional control rather than trying to control the surrounding environment.
The rider coming up behind was an idiot but I’m guessing there may be more to the story. Did the rider of the hot young horse have a history of needing everything just so? I am also aware of conflicts between riding disciplines. Dressage riders in particular can’t seem to handle a reiner galloping past in preparation for a sliding stop.
With the basic info given, it sounds like the rider’s behavior was reckless and provoking.
Regardless, the handler in question was right to move to a facility more appropriate to their needs.