Radio 'altercation' with ATC

91.123 Compliance with ATC clearances and instructions. (b) Except in
an emergency, no person may operate an aircraft contrary to an ATC
instruction in an area in which air traffic control is exercised.

Presumably, the approaching aircraft was in Class E airspace, which is
defined as controlled airspace. Doesn't that obligate the pilot to
follow ATC instructions given to him?

Even if it were Class G airpspace, it's a de facto "area in which air
traffic control is exercised," by the fact that the tower controller is
providing service, and the regulation applies.

It's a given that you have to establish 2-way communication (or make
prior arrangements) before you can enter Class D airspace, and it
follows that if you're not going in to the airspace, you don't need to
contact the controller.

.... but once a pilot contacts a controller, isnt' he obligated to
comply whether he's in that controller's jurisdiction or not?
I can't recall any regulation that indicates otherwise.