A: If God does not exist then Life is absurd.
C: Consequently God exists.
C follows from A by reductio ad absurdum, while for A consider, e.g., that you are camping, and that lions are about to attack your camp, so you dress up as a ballerina and dance the tango with a twig, in your remaining moments. Clearly that would be absurd.
But if God does not exist then there is nothing that we can do to avert the terrible, inevitable extinction of all that matters to us. We can have no possible saviour if we had no greater Creator than the natural selection of random mutations amongst the rocks and stones. And if we are too petrified by that terrible fact to act at all, death will only come the quicker, so we must live as best we can, and act on whatever whim takes our fancy. To live is so to act, and furthermore we must do so in a world that will soon be lit up only by alien lights, as our own are extinguished.
We will not be remembered as who we knew ourselves to be, for all that we inhabit a world that is surely as we think it is, rather than as, say, the ancients believed it to be. Were the ancients just as they thought they were? Of course not, so consider what will ultimately be known of us by the alien language-users of the future? Might not we be no more than twigs to them? Now, although that ‘proof’ was admittedly not a very convincing reductio, it does raise some interesting logical questions.
E.g. if God's nonexistence is prima facie absurd then ought not the burden of argumentation to lie with the atheist? But how could we find good physical evidence of God's nonexistence? Cf. how, from a grainy photograph, we can't tell if we're looking through a microscope at Michelangelo's David, or through a telescope at a meteor (not without the bigger picture), or how, given only a short sequence of letters, we would be unable to tell if they were produced by monkeys on typewriters or by a brilliant crytologist.
(The following paragraph was added on May 9:) After all, empirical evidence, even of quantum mechanics, need not undermine belief in the existence of this Universe—we need only say that that is more or less how this Universe appears to be (maybe pausing to do some philosophy, to reflect upon how we represent our representation of it to ourselves). Similarly nothing within any sequence of words would necessarily undermine a justified belief in the existence of its author—perhaps its author is Joyce, or a Surrealist, or an alien and so forth (that its author is not Austin might of course be strongly indicated). And I have yet to discover why saying that finding no miracles, for example, might amount to finding evidence that this Universe has no Creator is so dissimilar to saying that finding no typographical errors might indicate that our string of words had no intelligent author (which is absurd). After all, even if there were unnatural events, scientists could hardly accept any evidence for them as more probable than its deceptiveness, whence (what Dawkins consistently avoids) the absence of scientific evidence could hardly imply the non-existence of the unnatural.
Another interesting logical question is, if atheism is true, then why should we care about (what we have somehow come to think of as) truth to the extreme of challenging major political blocks within our own society? And a more metaphysical question is, what’s so wrong about absurdity anyway? Why not embrace, say, paraconsistent logic, or Humean Supervenience?