Hope It Succeeds
I hope the site succeeds, although not necessarily on its own terms. By its lights, Left2Right is about engaging the Right in order to persuade. I think it's more likely to have its assumptions exposed by the Right, forcing members of a largely homogenuous community to defend themselves in a manner to which they're unaccustomed. Most of the time in the academic community, they have to defend up; that is, they present a refined idea on top of a host of belief and data and have to further refine the idea in response to objections. But in an enterprise like this, they'll have to defend down; they'll have to reexamine the foundations on which their "common-sense" or "neutral" beliefs are based (that is, if they'll engage enough to do so instead of demanding that all discussion take place on their "home turf.")
But it's good for them, though, and maybe it'll start a kind of critical thinking on the Left that it's lacked so far.