I've recently had an eye-opening in regards to resistance (as uke) during techniques, and I'd like to share: Uke aren't punished by good technique, they punish themselves. And, IMHO:
"Resistance is Futile (for Beginners)."
Beginners need not apply... resistance. Unless they have a good henkawaza ready. And henkawaza is properly understood to be advanced technique... so, again, beginners need not apply...henkawaza
As a training partner, especially working with beginners, my objective should be to help the other person to learn the technique be practiced. Sometimes by modeling modeling the proper ukemi, so that they can model the proper technique -- and this method may require that I resist ineffective technique by guiding it where it should go. Again, IMHO.
In honest practice, with advanced students, I should NOT be anticipating, but attacking and then reacting... Hankewaza and/or ukemi happens as a result. And if the resistance occurred, it should be of the passive type -- either I was not being lead effectively, or I was being lead too fast for my comfort.
Resistance is a two-edged sword, that cuts both ways. Resistance can allow you to save yourself from a horrible technique (two meanings, yup), and resistance can cause uke to further the scope of their resulting injury due to the escalation caused in part by nage's reaction to resistance. Both situations should be discouraged, especially for beginners.
Of the two types of resistance (active and passive), I am of the following opinions in regards to basic aikido practice:
1) If a technique is properly executed, active resistance causes more pain and possible injury for uke: Examples: nikyo, sankyo, hiji-gimi, or most any properly executed lock. Why condition your ukemi reactions to encourage self-destruction?
2) Passive resistance is what happens when uke doesn't move fast enough to take proper ukemi, or when nage is not properly executing the technique. As uke, this means you're not moving because you are not being lead, or you are slowing down the execution of technique to CYA and reach the mat with minimal damage. Either reason is fine, as long as you recognize that it is educational -- for you and/or nage. Try to harmonize so that there is no passive resistance in the blend of the technique... discourage the opportunity for the resistance to occur.
3) In regards to dynamic aikido technique, active resistance on the part of uke is counter-productive (yes, I see the pun): Aikido practice usually occurs at less-than-realistic-attack-speed... when things are moving slowly, it is possible for uke to (a) anticipate, (b) recognize what the technique is trying to accomplish and (c) have time to apply some form of counter-intent. As the speed picks up, the opportunity for uke to resist shortens drastically, even with anticipation and recognition acting in concert -- to actively resist a technique requires that you know what the technique is trying to accomplish. And it becomes even more dangerous for uke at full-out, balls-to-the-wall attack speeds, and is even less likely to occur without resulting in injury.
Ride the edge, yes, but not to the point of self-destruction. Henkawaza is not resistance, per se, in my book -- it is finding a weakness in a technique and exploiting it -- riding the edge of the sword until you can grasp the handle and use the sword. Beginners are still trying to see the point, let alone the edge, and they haven't yet realized they can grasp the handle; they shouldn't be encouraged to do so except under very controlled conditions.