Justified?

So it happened like this. I'm at work on Friday, and go to visit the loo. Another co-worker is in there as well. A woman enters with a crying child. Co-worker exits. Woman apparently does not know I am there and begins to beat the child. Child is pleading "please don't beat me again" and I can hear this woman wailing on the kid. I quickly come out of the stall, surprising this woman who has her arm drawn back, hand in a fist. Without thinking I say, in a surprisingly calm voice, "Hit this child again, and I will kick your ass." I then turned my back on her and proceeded to wash my hands. She says "I'm just disciplining him." to which I reply, "That is not discipline, it's abuse and it's unacceptable." I dry my hands and exit the loo.
I'm pretty shook up, cuz this kid broke my heart. And I've just both honored and violated my own code of ethics. Honored, because I believe that protecting children is the responsibilty of every human being on the planet. Violated, because I am truly a pacifist and using violence or even the threat of violence is not who I am. Conundrum.
This woman has the audacity to complain about me to my supervisor, the manager of the pet store my hospital is in and the corporate offices of both businesses.
I find out tomorrow if I will be written up, suspended or terminated for my actions. The only certain thing is that I will be punished.
I figure either way, something good has to come of this, right? It can't be a karma strike against me.
I may soon be joining the ranks of the unemployed, but hey that'll make four of us, won't it. At least I'll be in good company. Deserted island anyone?