I have studied in several schools for extended periods of time and have experienced those that preach absolute non resistance and those that preach strong resistancewhile training. Both, are hopeless, in my opinion. You need to train in-between most of the time, and from time to time, go to either extreme (not just a bit, but a lot at either extreme, then back tothe middle).
The middle road - very Buddhist in its wisdom. Not really sure what it is about Aikido and those that like to comment on it but it sure breeds a lot of extreme statements. I've seen this in the resistance game, but also speed vs static, name your concept.
Aiki in my view really reflects an increased sensitivity to your opponent. The ability to respond to their energy in a way that makes it your own. If there is no resistance during training then you can not experience that energy and learn to utilize it. Conversely if you are always working with hard resistance you will never learn to overcome that energy without an equal measure of force.
I think you two really nailed it!
Sometimes you need no resistance, sometimes you need a ton, and most of the time you need a little/bit.
Training constantly with no resistance, is like training Karate and only ever doing the kata's, and expecting students to be able to survive a kumite later with only that. Likewise, full resistance would be like doing Karate, and only doing full-contact from day one, and still expecting the students to learn the details of the technique.
Both extremes have their place in the training regiment, but with just a bit of both - and a whole lot of in-between.