Re: causing no (serious) harm
Perhaps if Rob could provide more details I could provide you with my specific answer to your questions. As it stands, I of course would have to agree with what you are implying: Such things can be forced upon us regardless of our actions and/or our lifestyle, etc. You are right. The Shihan in question may be in such a situation. It is possible that the Shihan was in a "very bad" neighborhood (not in Japan) wherein gangs or groups of people attack lone folks passing by.
Still, I don't feel that this possibility makes it true that such situations in general are not so easy to avoid -- if you will allow me, after all your aunt does it on a regular basis. I am sure you do it as well when you visit. If you grow up in such neighborhoods, you learn how to do such things from an early age. In other words, it does not take us to be the "exemplarily example" before we can figure out how to avoid such things and/or to get quite good at avoiding such things. Thus, we can very early on learn how to keep such things rare and/or to keep such things as occasional realities.
True, they happen. True, they can happen to the best of us and probably have. But, for me, it does not become more consistent with a life of Peace (should that be your goal in life) to stop someone's head from hitting a wall than living a life wherein such things remain rare or completely absent. That was the point I tried to make. It is not the lesser of two evils that I was saying I would focus in upon when hearing the story; rather it was the greater of two goods. I was not focusing in upon whether it would be more consistent with non-injury to stop someone's head from hitting the wall or letting it hit the wall. I was focusing in upon whether it would be more consistent with non-injury to stop someone's head from hitting the wall or not being in a multiple attacker situation at all.
Out of curiosity, perhaps Rob could tell us more about the situation -- or at least if it happened in Japan or in the States in a very bad neighborhood??? Rob???