Of course I forgot to mention this, deliver any hit, kick with affection.If you have to chastise someone be firm but kind.Do not take it too personal.The other person is simply misguided.I think this is the essence of Aikido.To cause minimum harm to your enemy if humanly possible.Joe.
My back ground has been in from taekwondo-karate & hapkido (which, I believe, combines elements of karate, jujitsu, and aikido), my defense 'contacts' over the years have displayed restraint: None involved kicks (i manage to resist a wide open low round kick to his head after he got knocked down and I actually apologized to the aggressor, mostly in fear of the scary bouncers). In the most recent case, in a commute BART train --Richmond bound, mere jumping in the middle of a beating was enough (resisted the urge to come in with a hook punch) to stop that battery-in-progress, but felt glad to be ready enough, and that perp quickly waked away (I got lucky).
I used to think kicks were my assets until I started sparring with competitive UFC "fighters" and kyokushin-karate "fighters", both types of players employ kicks to legs, which made me realize the "cost" of kicking and the earnestness of staying in balance and sabaki movements.
I'm still sorting out the "..To cause minimum harm to your enemy if humanly possible..." idealism: sounds good, but at times, naive. That's my Zen koan: Is the killing of a psychotic Icchantika (http://en.wikipedia.org/wiki/Icchantika
) "blameless" since we are all Icchantika, in some ways. I agree with restraint, yet I have attachments to the notion that felons that have demonstrated selfish killer intent need not be granted mercy during the felon-in-progress.
Martial arts are fun way to holistic health, but if I spend the time I want to learn the practical, effective, ways, while balancing risks to injuries.