It's a theory that Besimudo came up with... the Sorceresses are the 'embodiment' of the power of the Great Hyne, creator and God of the world. Thus, the Sorceresses are 'divine'. Their knights, therefore, would be 'holy knights'. This means that Squall and SeeD are in fact fighting against the divine powers, so that they can be overthrown and humans can reign supreme

It's not what I believe, just a different way of looking at the religious side of FFVIII's plot.