How would have I reacted BEFORE the aunt's mom chimes in?
-"Kid! That's not the way to return the bottle to the table. Please pick it up and place it on the table the way it should.
Because, syth82, your kid didn't throw the bottle because of lazyness as you said, he just did that to show his displeasure for not being allowed to take the bottle with him. If it were for lazyness, he would throw dishes, forks, spoons etc all the time, even at home, but I'm willing to bet he doesn't, because he knows very well what's the right way to put things on a table. In your situation, the threat of spank was out of context in my opinion, but the kid needed some help to deal with his own frustration.
Maybe that's the point where you got confused and think that we the "spankers" are all the same than your aunt's mother and do that because we are unable to understand children, feel love, dialogue with kids etc, and that by explaining ourselves we just try to confort our own minds. The barrier between dialogue and spanking is very blurry and change from people to people, from level of education, income, etc, and obviously, from their own experience as kids.
Parenting is a magical thing, because it seems that everybody think he knows enough of it without having to be taught anything. I remember a mother of a girl that attended kindergarten with my daughter, complaining about how the teacher "didn't understand her little girl". Maybe so, it was herfirst daughter, but it was probably the 200th baby going though the teacher's class. The teacher may know a thing or two about kids, if only because of experience, and being isolated from affectional bias, she probably know the little girl more than her own mother. I have read many books about parenting, probably as many as about motorcycles. In neither of them support spanking, if only because it is not "politically correct", and I have always tried to put their teachings into action, but some of them didn't work. There are no magical recipes, some things work with some kids and some other don't, I have found that translated books doesn't mean much because cultural differences are inmense. I can't put into action many things about child education written by americans, when the education at school in Spain is so different that my kid would become a "rara avis". Education is very complex, it is made by parents, family, school, even groups of friends.
Sorry, I forgot you just wanted to hear that your aunt's mom was a prick. We haven't heard the other side of the story though. Maybe your kid misbehaved during the whole visit, like jumping on the couch and the like, and the old woman just got fed up that the parent wouldn't react and had to react herself.
I have had to leave because my kid was embarrassing me, and it was either spanking him in front of others, pretending nothing happened and know I won't be invited again, or admit my kid was not behaving appropiately and it was better to postpone the visit for some other time. There is nothing wrong with that.