I'll chalk that up as purely opinion, since that flies in the face of Gawd knows how many scoped muzzleloading rifles, let alone scoped centerfire rifles, that have been used for hunting inside of 100 yards ever since the advent of optics rugged enough for rifle use.
Bad eyesight, like my uncorrected 20/200, shouldn't be used as a discriminating factor over who should or shouldn't be in the woods with a rifle. That decision is best left as an exercise in common sense, chances are the individual with poor vision may have had to drive close to the hunting area, and needed legal vision for their driver's license, too. (It's called eyeglasses or contact lenses) Common sense also dictates that the shooter, regardless of their visual acuity, wouldn't think about picking up a gun and going hunting unless he could clearly identify his sights, his target, and what was behind or near his bullet's intended trajectory.
And if you want to beat up on the folks using optics on muzzleloaders at ranges past 100 yards, I suggest you go way back into the books and check out how effective Confederate snipers were with their .45 Whitworth muzzleloading rifles, outfitted with the Davidson scopes, particularly against Union officers who didn't think they could be targeted that far out...
