B767-300 Captain reported refusing an aircraft after loss of an electrical bus and repair could not be made prior to scheduled departure time.

Narrative

The situation was having both a generator and a BUS failure in flight. We were able to get the BUS back; but unable to reset the generator. However even with the APU as the second generator; we again had a BUS failure just as we landed in ZZZ1. The problem was MX Control; not the situation of losing the BUS itself. MX Control made every effort to coerce and second guess myself and my crew's decision that flying with a deferred generator and an AC BUS that was not necessarily steady over the North Pacific was unacceptable; and undue pressure to fly was unsafe. It took me terminating the phone call with Dispatch; MX and Duty Pilot to force MX Control into doing the right thing and grounding the airplane and fixing the problem. This was after I called the Duty Pilot right back and had a private conversation with which we both agreed that continuing was unsafe. This narrative of pressuring pilots to move metal needs to stop. I don't have a cause narrative here other than MX Controllers pressuring pilots to go. This has become enough of a problem that it is being discussed in recurrent classes now. MX Control needs to stop the narratives and become the supporting department they are supposed to be. Let's work together to fix the planes and keep the metal moving safely; instead of trying to only keep it moving steadily.