Bad bus behaviour

Yesterday on the bus I saw something which really annoyed me. When on my way back from Oxford Street another family got on the bus, a dad and his two children. One child looked to be 2 years and the other maybe 6. The kids were so loud and rude, screaming at the top of their lungs, standing and jumping on the seats, the younger one spitting on his sister and the seats. I have been in public with very "difficult" children and appreciate that sometimes there is nothing you can do to get kids to behave and that it can be very stressful for the parent.

I have total sympathy for parents with crying, screaming babies and children where you can see that they have tried their best to calm them down, I have been there myself. In this case, however, the dad did nothing to even attempt to get the kids to calm down. He did not say anything, he stood away from the kids and let them run riot. The only thing he did was to walk over, at one point, and slap the girl on her arm, with a few mumbled words. Without warning, without as much as a polite ask to behave. This astonishes me. So you say nothing, you say nothing, you say nothing and then you hit? Even for people who believe in smacking children as a form of discipline (which I do not) surely this is leaving out a few steps, such as a warning? Of course I don't think those kids were bad kids (I don't really think there is such a thing) and I have no idea of the circumstances surrounding this family. I just felt like if there is such a thing as bad parenting, this was it. Rant over.