Re: Train of thought
It's an argument over semantics you are making. When someone says training against resistance, they do not mean fighting the resistance. They mean learning how to use your techniques against a non-compliant uke. One who is not just throwing a single committed strike, but rather tries to accomplish a goal and does not stop trying to accomplish that goal until he is thrown/pinned/submitted.
I'd suggest reading some Matt Thornton to get a good idea of what I'm talking about. Obviously you would want to use proper aikido movements and techniques. The difference is that the uke is trying to stop you by any means allowed by the drill. This could mean something as simple as, keep trying to grab me, and throw me down until I throw you. Or it could be something as complex as come at me any way you want and don't stop until I pin you or you pin me (sparing).
So you can call it working with resistance, or against resitance, or whatever. The point people are trying to make is that if you are not training beyond kata training, with 'aliveness' as Matt Thornton calls it, then you are going to have problems using these same techniques outside of the dojo.
For more info on aliveness and matt thornton, try google, aliveness101.blogspot.com or bullshido articles.