Your argument is valid only because every false premise logically implies every true conclusion. For example: If the sky is pink with green poke-a-dots, then dogs are mammals.
I think that means his argument (and your example) is a Non sequitur and is thus illogical and meaningless regardless of the truth or falsehood of it's individual components.
As for the Sun, it has intrinsic properties that giving off light that heats the earth. Our valuation of a bright and warm Earth are subjective even when they don't have a bearing on our continued survival.