The lady with the Bronco doesn't care why you helped her. You helped her. Even if you had just been looking to get around her, in a city full of saints, you were her angels.
One thing we human beings are good at is invalidating the good things we do. It's hard to be with our better side, because we're so much more familiar with our negative side, so much more comfortable there. So we pull out all sorts of weird things to take the good things we do down a peg or two. "Oh sure, I did that good thing, but it was really just because of X". It's the same impulse that causes us to play down compliments and say things like, "Oh, this old thing? I've had it forever!"
Also, Hal, motives are definitely admissible in court. The difference between Homicide and the various degrees of Murder is the motive of the act.