Two sides of the same coin. Aiki is, ultimately, about unification. Time for Aikido folks to end this war and realize that development of both aspects of Aiki are needed for the practitioner to become adept at the art of Aikido.
Place the immovable body in the midst of a crowd of attackers and the result will be an immovable stain on the ground. Likewise, technique executed by simply mimicking the movements of the instructor without the application of power that comes from a unified mind and body will result in an honest uke moving through nage like fire through a field of dry wheat.
Both sides in this debate bring added value to the table. Time has come to abandon the dogma that characterizes entrenched positions and approach Aiki in a holistic manner that recognizes its multifaceted nature.
I'd note that nobody has argued against the validity or utility of moving around, evading, jumping, dodging or any related action as a martial tactic. If you watch Shirata (the source of that "immovable body" quote) you'll notice that he moves about quite a bit.
The difference of opinion comes as to what the definition of "Aiki" is - saying that "Aiki" isn't evasion doesn't mean that evasion is wrong, or even inadvisable. Donuts aren't "Aiki" either, but where would my day be without them?
To the people who think that all definitions of "Aiki" out to be accepted, that it's all good, what if I said something like "I was walking down the street and I turned to a teenager who was annoying me, kicked him in the nuts and broke both his arms, what wonderful Aiki!". Wouldn't you feel obligated to say something?