What I've been reading

I looked at this post on BlogHer because I expected it to be a parody or something. Now, before I get into what the post was about, read this exerpt & decide what you would think & do if you saw this situation in real life:

Say I’m in a McDonald’s. In a booth near me is what appears to be a romantically involved man and woman enjoying a meal together. Near the end of the meal, the woman accidentally knocks her soda over and it spills over the table and floor. The man leaps to his feet and yells, “Oh my god! I told you to be careful with that!” He grabs her by the arm and drags her out of the booth. “That’s the last time you get to have a medium drink!” He shoves her off to the side while he starts to clean up. “Go stand by the door, we’re going home right now!” After an initial little gasp at the spilled drink, the woman remains silent, body slack, eyes averted. 

Issa asks what if it was a child, not a woman? Her analogy really hits home because I've often seen parents/grandparents/caregivers do things like this with children in public. A few months ago when I was walking through the parking lot in a suburban mall, I saw a little boy & an older woman that I assumed to be his grandmother. She was yelling at him for something & spanking him with one hand, while gripping his arm with the other. A person walking near me intervened, saying "You don't have to hit him! He's just a little kid!" I have to admit that I walked on, unsure what to do, if it was my business. I also wondered if it was really worth getting involved because, most likely, no matter what I said, the woman would get defensive. How useful would it be for me to say anything? Would it change her mind?

Have you ever seen a stranger hitting a child? What was your reaction? Do you think it's appropriate to intervene & if so, when or how?