I have no idea whether John McCain was in the "cone of silence" during Barack Obama's chat with Rick Warren and I don't much care. What I do find interesting is the fact that the Obama campaign has chosen to make the question such an issue.
There seem to be two difficulties for Obama. The first is that choosing to emphasize the issue is essentially a concession that McCain waxed him. People who did not and never will see the event now have the impression that both candidates sat down to discuss faith, morality and politics with a popular and apoliticial religious leader and that McCain was far more impressive.
The second is that it's another example of what seems to be a tendency to prickly arrogance on the part of Obama. You beat me? You must have cheated! Nothing else is conceivable.