I'm taking the heli pilots side in either case, but learned that unlike airplanes that have to adhere to flight plans, altitude mins, etc. The helicopter can fly almost anywhere.
Right, but not usually over parks.
From the FAA website.
91.119 Minimum safe altitudes: General.
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Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.
(b) Over congested areas. Over any congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.
(c) Over other than congested areas. An altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.
(d) Helicopters. Helicopters may be operated at less than the minimums prescribed in paragraph (b) or (c) of this section if the operation is conducted without hazard to persons or property on the surface. In addition, each person operating a helicopter shall comply with any routes or altitudes specifically prescribed for helicopters by the Administrator.
They generally have a map with minimal altitudes on them, they are for example often allowed to fly 500 feet above populated areas, whereas other aircraft are limited to 1000 feet. They would be allowed to land in those areas and that would be the only time they would be allowed to fly below 500 feet. They should not fly directly over areas where they know model airplanes fly, In accordance with the part "without hazard to persons or property". Of course the helicopter in question may not have known about this, but your helicopter pilot did and he should have stayed away, or slowly approached from the flightline side to observe if model aircraft are in the way. For him to assume he should quickly fly over without looking because he had the right of way would be stupid.