No question here. It is their sky and we are the interlopers. Give the masters their due and retreat. I certainly would not want to risk tangling with a bird and causing him injury or death when I can leave him in peace. There are any number of reasons why a bird might get aggressive. Best course of action is to leave them be.
All my experiences with birds have been pretty good. Most don't seem to mind my sailplane joining in, circling in a thermal. One rule of thumb is to turn in the same direction. I have had a couple of Turkey Buzzards and a few Redtails fly in very close formation, obviously curious, but have never have seen any aggression.
I have been chased by Redtails on the slope a few times, probably during the nesting season. A dive and quick change of direction has always worked and they have never pressed home the attack. Talons will usually do a number on Monokote and balsa!