One problem we face is that many attacks are not for 'justifiable' reasons but are people who want to look macho (usually young boys trying to prove themselves in a pecking order) - even the police man; just as you can sometimes find in a dojo. How should you react? One school of thought is to avoid problems by whatever peaceful means possible (as illustrated above). This may help you, but does it help the perpetrator or his next victim?
For example, I was subject to an unprovoked attack by a bouncer, who I managed to remove from my neck as well as dissengage the other boucer friends that came up to help him. The police arrived and it all worked out OK as the police believed me (though would take no action) and no-one was injured (few scratches). However the bouncer who attacked me was very shaken and is likely to re-consider attacking someone half his size again.
Maybe this is wishful thinking, maybe he just spent more time down the gym and practising self-defence so he could destroy his next victim. If you respond physically to a situation you get 3 long term responses:
1. agressor beats you up and feals good about himself and is likely to continue this behaviour
2. you beat up the agressor and he is so ashamed he never picks on anyone again
3. you beat him up and he toughens himself up for the next encounter, becoming even more bitter.
Aikido is like the second option, but without the injury. Although Aikido is 'non-agressive' there is nothing more anoying to a bully than someone who manages to evade his attack in a harmless way. You can just hope that on reflection he will change his ways, or you may be required to give him several atemis to illustrate the futility of his attack.
If you respond verbally to the situation the perpetrator continues with the same attitude. As an Aikidoka I firmly believe that we must interact with our environment and people in an intimate way in order for the flow of ki to pass through us and the universe. In addition we should accept death as part of life and sometimes necessary to achieve harmony. Harmony isn't staying alive, it is achieving peace.
(if Ueshiba wanted to escape death rather than to achieve harmony he would have learnt to be the worlds best sprinter rather than a martial artist. Aikido enables people to be truthful and upstanding members of society without fearing retribution from those who would persecute us.)