When you explain complicated concepts to an extraterrestrial, or a time-traveler, or a child with no frame of reference, you must boil the idea down to its simplest elements. But sometimes doing that reveals that the concept itself makes no sense! Maybe we should do this sort of thing more often. Link
That said, the ethical situation gets trickier when rules are not enforced, not enforced equally or if most or all participants are violating them and getting away with it.
As for fair, what about all the technological advantages rich countries have over poor ones - better training facilities, better equipment, financial support, scientifically formulated diets. If we are going to be truly fair shouldn't all athletes have access to the same training and equipment.
Where does one draw the line.