“We are also making an outrageous proposal: that the church in its contemporary, institutional form has neither a biblical nor a historical right to exist.”
“In short, this book demonstrates beyond dispute that those who have left the fold of institutional Christianity to become part of an organic church have a historical right to exist.”
I think there's a really, really big difference between statements of the first form and those of the second. In particular, on those occasions when I attempt to lay down my self-righteous smack on issues related to church leadership, polity, structure, etc., etc., I hope I always mean to make statements of the latter "Y is [also] valid" form - though without the whole "beyond dispute" hubris - as opposed to the former "X is invalid" form. I do feel that certain aspects of our contemporary institutional church that are almost universal - including many of the ones examined by Viola and Barna - probably ought to become (by contrast) almost nonexistent in the postmodern world, because I think in more and more contexts they will do more harm than good. But I think context is everything, and I think that things like (for example) church buildings, clergy, sermons, seminaries, hierarchies, etc. have been and still are appropriate in many contexts - but probably never should have been as universal as they became. And, I suspect the contexts in which they do more good than harm are becoming more and more scarce.
But anyway, my main point is that I hope I avoid making statements like "X has no right to exist" when I really mean to say "Y, though different from X (and despite the near-universal assumption of the need for X) does have a right to exist, can work, etc." If you catch me doing the former, please smack me down. Srsly.