I've trained over 20 dogs in my own home and volunteer at the shelter. A pop is different than hitting. Not to mention a take down when they are overly agressive has been needed on several occasions. Or are you going to tell your dog to take a time out when he is snarling at your kids? BTW, 7 of those 20 dogs are in homes with kids rather then being put down. Of the 20 only 1 didnt make it out. My techniques are not 100% garanteed to drive results, but I was taught them by a certified trainer 7 years ago so I know its not something I'm pulling from left field.
To answer the second part.. I stole from a store when I was 8.. my mom beat the mess out of me and I have never stolen anything again to this day. So I guess I'm proof that it does work huh??? You dont have to spank kids, and over using it is extremely bad... but if my kid thinks its funny to lay in front of cars as a game I'm going to make him wish a car did hit him.
What all of you know it alls are leaving out is the fact that everyone needs to be trwated different. There is no cookie cutter way to discipline your kids. You find what works for your kid and adapt as they grow older. If you only spank your kids it will get old.. the same as if you always send them to the same corner or take away something. Find what works and use it.