True, but being that guardians have been corrupted in the past and are able to be taken over by the flood (not counting light, as far as we know) they have no reason not to be. And there is nothing that says the light would burn anything away. Guardians still get sick, and the flood is just another parasite

Nothing that says it wouldn't either.

Ok not gonna be rude but that's a logical fallacy, shifting the burden of proof. Your argument is like someone claiming that Bigfoot is real, when challenged he says "prove he isn't real." It just doesn't hold up. Unless the lore specifically says the light will burn away anything that tries to corrupt a guardian (which it can't since Dregden yor was corrupted by the darkness) then there is no way of knowing

No I'm saying it's impossible to say either way. At this point in a new game world we don't know the extent of the lights power.

Ok, so then we'll just agree that until further explained, there is nothing holding the flood back from corrupting them. Sorry, but that would be the logical conclusion