So far, we know of three "forces", or forms of energy, in the KH universe: Light, Darkness, and Nothingness.
Now, darkness in its purest form leads to, of course, Heartless.
"Nothingness" sounds like it should be just that - nothing - but we know it actually is the domain of the Nobodies. (So I guess from that perspective it makes even more sense to say Nobodies shouldn't exist... hadn't thought about it like that until now.)
And light in its purest form makes... what?
Well, if the Princesses of Heart are any indication, then light doesn't make any type of monster. A person full of light is still just a person. In fact, it seems that light is sort of the "default" standard for humans, and that darkness is required to corrupt a person into something else.
So that's why I don't like these ideas that light is what the BBS enemies are composed of. It just doesn't make sense, light doesn't corrupt people at all, we have proof.
Hmmm, yes I see your point. I never thought they'd be made of light either.