If someone says that a statement is capable of being if and only if it is logical and supportable through evidence, then the term "logic" in that sentence isn't referring to soundness of premises, it is referring to making good inferences. How do I know this? Because evidence is how one goes about establishing the truth of most premises. If the term "logic" in that sentence encapsulated the notion of having true premises, then there would be no reason to refer to evidence at all. At the same time, it would be the most trivial thing to say ever. Logic, then, just means "capable of being reasonable." And if that is all that is being said: That propositions are only meaningful if they can be reasonable, then, "Duh!!!!!!!" Holy obvious Batman. But, that's not really what was being said. This can be figured out from the dicussion on evidence that follows. He's trying to explain what it means to be reasonable. According to him, being reasonable entails using good logic and having evidence. This, however, can't quite be right for some reasons I listed above.
What I find interesting about this entire set of threads is that we have now gone from the secular materialists here digging in their heels and determinedly refusing to see what in essence is, once you've worked you way through the argument, a fairly clear cut logical contradiction regarding Dawkin's claims about the world and value judgments within it, to a full blown argument regarding utterly straightforward principles of deductive logic that any Freshman philosophy course would have covered within the first couple of weeks. Mercury telling Light that he doesn't know what he's talking about, when Merc clearly doesn't even understand the first principles of critical reasoning, is roughly like telling Godzilla he doesn't know how to break things.
I find the fact that an actual argument about rudimentary principles of deductive reasoning fascinating, if only because it demonstrates how critics of the Church, and theism proper, will go to any lengths and challenge even established canons of intellectual discipline to preserve their onw metaphysical beliefs and assumptions.