Don't run the engine when low oil pressure is indicated.This is not confined to BMW R models or any other type of motorcycle or vehicle.
Any internal combustion engine should be shut down when low oil pressure is indicated.The fact that your moto's low pressure warning light shuts off when the idle is increased could mean a few things—a low engine oil level, a defective oil pressure switch, a defective oil pumpor oil intake blockage, defective engine bearings. An engine in good condition regardless of whether it's an R or K should idle somewhat below its spec without indicating failing oil pressure unless defective oil pressure switches are endemic to the model, in which case they should be replaced with reliable switches.
I'd be investigating for a defective oil pressure switch first. There are a couple of good Airhead forums where you could find consultation—
this one and
this one over here.