I've seen "run-away" show up many times in several posts. In Aikido, running away isn't suggested or implied unless facing a life threatening situation from which the only recourse is to escape. There is a large difference between running away and avoiding a situation; recall Marubashi.
As well, remember that violence is fueled by intent. When someone attacks you, it is impossible for you to be attacked personally. They are not attacking you, because you don't exist. If you take an attack personally, then you are biased and personally invested in the attack. If you exist, if there is an awareness of the self, then you cannot be part of the attacker's spirit.
The attack is just a motion, just an action in time and space, and when you dismiss self, your action is simply the response, the purest movement to counterbalance the attack. There is no anger, no life or death, no here and now, only the Universe within and around you that embraces the initial movement and resolves the issue.
The attacker should have an option. If you extend your fist, and the attacker decides to run into it, then it is his suicide. If he chooses to stop the attack, then there is no more action. If you FORCE the attacker to do anything, then you are imposing your own energy and bias upon the situation. If you are purely void of self, then the attacker will do it all on his own.
So, yes. If the attacker runs into a wall and breaks his hand, it is his own fault. But our purpose in all purity is to resolve the situation so that NOBODY is injured. Pain is useful; damage is bad.