Skill and vocal range requirements are not discrimination

Great and wise and mighty and terrifying the ophanim may be, but melodious they are not. Their voices sound like "waves of the ocean, and when they spoke, it [is] the noise of thunder and trumpets" and there just aren't that many compositions that call for that particular register (except for Bach's Toccata and Fugue for Strings, Drums, Waves, Trumpets and Thunder). Not many SATBWTT choirs out there.