SHO-RUYKEN!!!!!
Seriously, without knowing more I can't really comment except to say that at that moment in time, it didn't look like the bus driver was being physcally threatened.
However, on the whole philosophy about striking a woman, here are some of my thoughts:
I personally think it is wrong to strike someone; anyone, unless it's self-defense and only as a last resort. I also think that if we are to hold true equality of the sexes and the de-facto way of thinking and operating, then equal has to be equal.
As such, I would look at striking a woman as i would striking a man that is approximately equal to said woman, physically. That is, they might or might not be a viable threat given their physical size or fighting skill, but if they are attacking me with reckless abandon then yeah, I will defend myself enough to deter further attack. Just because one is female and suposedly the "weaker" or "fairer" sex, it does not give them a carte blanche to attack someone physically without fear of reprocussions, nor should it.