I'm just going to go ahead and throw this out there. According to a study
2007 study, roughly 50-65% of parents of preschoolers and toddlers use corporal punishment (spanking, etc).
http://scholarship.law.duke.edu/cgi/viewcontent.cgi?article=1565&context=lcpI'm sure there are newer stats, but that's what I have right now. If you're going to use stats, use relatively up to date stuff.
If done with respect and out of love for you're kids, I have no problem with spanking. I was spanked. I don't remember why, but I suspect it's because I didn't do it again. Most of my friends spank their kids and I'm pretty sure I will when I have kids of my own. It was and is (with my friends) always done out of care and correction and is followed by words of affirmation and love, and often a hug.
I'm currently a social worker working in child protection. Absolutely there are people who go too far, but that's why I have a job. There are bigger, far more serious issues with kids than spanking though.
Take neglect for example. If neglected in the first two years of life, a child is more likely to have increased levels of aggression when they are older than if they where physically abused, or physically abused and neglected.
http://pediatrics.aappublications.org/content/121/4/725.full.pdf+html
I'm not going to be a harsh disciplinarian when I have kids, but there are definitely going to be times when I am not negotiating. If that means they go to their room, lose some privileges, or are spanked, so be it. I am not debating with a 3 year old about what is ok and not ok.