And, by the way, we have had the debate--even, arguably, in the midst of a crisis. This was all over the news for weeks after the shooting in San Bernardino when the FBI told us it was vitally important to gain access to the perpetrator's phone. They didn't get their back door. Legislation was proposed that would have required it, but it was never adopted. (Though, in fairness, FBI did supposedly get a private company to break the encryption. But this was only after a very long delay and after all the public debate had largely dies down.)
Barr's point is that it's better to have that argument now, in a level-headed moment and with opportunities for all the relevant stakeholders to provide input, than it would be to have it in the middle of some dire emergency.
If you oppose back doors, I would think you would agree with him on this -- government tends to be delegated sweeping powers in emergencies, so it would be much harder to stop gov-friendly proposals like "back door all the things" in that kind of moment than it would be to stop them now.
"We must do something now, it's clear that we need backdoors because of X!" <- That's a much worse position to be in during a debate.
