I just want to make it clear that (I hope you are saying) that the bonehead decision by Duke and UNC was continuing to persist in their opposition to expansion after it became clear that the result of this opposition would be the admission of Virginia Tech and not Syracuse.
IMHO, the original decision to oppose expansion was far from boneheaded ... it was absolutely right.
Expansion had so far been a disaster for the ACC in competitive terms (we've yet to see the promised second BCS team; the football championship game has drawn pitifully small crowds and attracted little attention; basketball has been seriously damaged by the loss of the balanced schedle ... I'm not sure the recent decline in the league's basketball performance is due to expansion, but it's an interesting coincidence). Financially, it's been a wash -- true, the league signed a big new TV deal, but with the added split (12 ways instead of nine), the per-school payout has been very close to the same.
As for the law of unintended consequences, raiding the Big East for three schools forced that league to adjust by bringing in the likes of Marquette, Louisville, DePaul ... and as a consequence, it's become better than the ACC in both football AND basketball since the ACC's expansion.
As far as bonehead moves go, expansion as a whole is far, FAR worse than the tactical blunder that Duke and UNC made in opposing VPI.