Re: Why bother keeping Aikido 'pure'?
While an overly compliant uke can certainly be a problem, I think people who say that it's unique to aikido aren't paying attention.
The first time you spar with a live partner in a karate dojo, does the senior student beat you bloody? No? Then I guess he's being "compliant," huh?
And as pointed out up thread, it's kind of hard to train lethal or crippling techniques any other way: you run out of partners really fast, and local law enforcement tends to get involved.
The question is how to ramp up the intensity and the "resistance" (not really the right word, but it'll do) so that students learn to handle progressively more realistic situations, while keeping the stress level low enough to allow learning. It's a hard problem, and I don't think aikido instructors are alone in struggling with it.