I would have loved to see the Leap Manifesto throw a personal challenge at supporters. I know it's a "top level" plan, and therefore a bit vague on details, and mostly concerned with systemic or social problems, but all the same, plenty of GHG emissions come from individuals, not "society".
Maybe something like "If you've read this far, and you're nodding in agreement, then show YOUR commitment by cutting your own carbon footprint in half. Walk, ride a bike, carpool, shop less often, use a blanket instead of the furnace, vacation within 100 miles of home, sell your car and join a car-share program -- do whatever makes sense to you to do. But if this is an uncomfortable idea for you, or you feel there's simply no way for you to do this then what do you believe you're supporting here? What were you nodding in agreement with?"
It's easy enough to support lofty plans that say "we must all", but if "we must all" do or not do whatever then there's no time like the present to start practicing for that. It's not like old habits are going to be easier to break later.