There is absolutely nothing resembling "fair chase" because one is using open sights. Fair chase is the method of pursuit, not the weapon used. A scope can be used for a precise close shot although up close, I prefer open sights.
You may be refering to the challenge created by open sights. Open sights can be excceptionally good if they're sighted properly and you practice. A couple of decades ago with good eyes, shooting an improved 375 H&H and a 54 caliber black powder rifle using conical bullets in the black powder rifle and using open sights only, using a rest, I shot clover leaf groups at 100 yards, with hot loads mind you, with both of these rifles. Nowadays, I'm not sure I could repeat these groups. I competed in shooting disciplines and shot six rounds of medium hot loads in a six inch 44 magnum at 100 yards, standing and with open sights, unsupported, in a 2 1/2 inch group. Open sights are not a hindrance nor are they the challenge you perceive them to be.
A real challenge is bowhunting with traditional equipment. I practice more with traditional bows than with rifles and handguns. Not all my rifles are scoped, none of my handguns are. It's easier to shoot with optical sights but it's as much fun to shoot with open sights; it's a matter of practice. Anyone can achieve a good level of proficiency with good practice. While competing, I shot with some of the best shooters in the country and received some of the best advice possible. What Mark Sullivan thrives on is closeness to dangerous game before shooting which is probably a bit easier with open sights because of the peripheral view afforded. Not to take anything away from him but open sights are not at all a return to the cave.
