... it seems to me that pain is a necessary element of learning the martial arts ... it seems naive to me to beleve that we can learn these things painlessly.
Yes, sure that is true. Pain indeed is part of the way of learning.
But from a certain techniqual level on it's no longer a needed element of good technique. As long es aiki-techniques are concerned.
Learning to deal with pain sure is part of living budo.
But also to be able to deal with and to controll an attacker, whether he reacts to the pain you inflict to him or he ignores it.
To rely on pain is very treacherous.
Once we have these things, we have the unique opportunity to be actively peaceful; it is no act of peace for someone to disdain violence who fears pain and has no capacity to cause it.
To rely on pain or not is not a question of being peaceful or not. It's a question of whether your technique works by itself or not (which means ~ has to rely on pain.)
In our dojo we some sayings like: "Well, your technique hurt's like hell. But it doesn't work." Or "I only had to move because of pain. It wasn't your technique that move me."
If you once have moved and controlled a drunken person or drug addicted person or even a mentally disabled person who all of them have a pain tolerance not comparable to what you experience in the dojo, you might understand, what I mean. No question of being peacefull. Just a question of what works and what does not.