I am a part of that audience and it's not anti-Facebook, but anti-(intrusively-social), which includes G+. Perhaps even at a higher spot than Facebook.
Maybe they can capture part of the anti-Facebook audience.
They would never get the anti-social-network audience, though. And this, which seems trivial, is important, because (for me) it's not that I am anti-Facebook, it's that I would never spend my time on a social network.
Besides, the same arguments that goes in an anti-Facebook opinion, are relevant also for g+
Sort of what those Mac commercials did by comparing themselves against boring old Windows.