Purely Positive Training

Okay, here comes another topic that may well get me in trouble with some of my friends.
I was there at the very start of positive training, back when clicker was first being introduced by Karen Pryor and Gary Wilkes, when Ian Dunbar was popularizing puppy classes, and the first feeble thoughts of forming a trainers' group were in the air. And since then I have trained many a dog with clicker or with lure and reward. And the results are great. And I will continue on this path. But. . .
There are a number of people out there who claim to be "purely positive," using no punishment of any kind. And here I have to take a stand. Because I don't see punishment as a bad thing. In fact, I see punishment as completely necessary, in its place and done correctly.
By punishment, I don't mean smacking the dog or using electric shock or throwing the dog on his back or any of the old-school forms. In fact, I have found that using punishment only when necessary allows you to use a much lower degree of punishment than if you were using it all the time. A slightly raised voice will absolutely crush my dog, and is all the punishment he requires. But make no mistake, it IS punishment.
Without punishment, there are no consequences, and all those people who claim that positive training doesn't work if you don't have a cookie in your hand have a point.
A low level of stress actually increases learning and improves performance. So being aware that punishment may happen for non-performance may also increase accuracy.
It's all a balancing act, as with most things. Initial learning should take place in a positive atmosphere. It's silly to punish for non-performance of some act a dog doesn't yet know should be performed. But once a behavior is trained, what are you going to do if you ask for it and it doesn't happen? Without some consequences, the behavior could eventually disappear.
Rewards and consequences both have a place in the world.