To echo some thoughts...
1. Resistance and countering are different. Countering and kaishi waza are different. We need to make sure chastising "resistance" is not chastising countering or kaishi waza. We also need to make sure uke understand when countering and kaishi waza are and are not appropriate.
2. Resistance is an indicator of improper kata. The more I hear good aikido people describe technique, the more I believe that resistance is just a product of poor kata. I like the thought of moving away from the notion of "non-resistance" and into the notion of "Did you see sensei push against uke? No? Well, then you are not moving correctly."
As for the original post, I believe each dojo has its own level of "opposition". Uke plays an integral role in learning kata and practicing waza. I think its important to express where your dojo stands and how students may train within the established levels of opposition. When in Rome...