You know, before I had kids and when DS was a baby I loved the theories on alternative discipline - no spanking, logical consequences etc. It all made loads of sense. DS as a toddler responded pretty well.
Then I had my first DD when DS was 18 months, followed 18 months later by my second DD. By the time DS was 3 I had a newborn and a toddler to deal with. DH worked a lot, I was often the only one home with all 3. DS was great at 2, but more difficult at 3 and 4. The DDs were fairly easy as kids go (well, the youngest could be a challaenge at times!). But I found that it was very difficult to implement this alternative parenting with 3 little ones! None of the books tell you how to juggle 3 little kids while doing this! And I also discovered that for reasoning, logical consequences etc. to work well enough, you needed to be proactive; meaning, you had to prepare your child for situations, lots and lots of teaching was involved (which is a good thing, don't get me wrong!), and when they chose to behave badly, sometimes the consequence that had the best teaching value was time consuming or difficult to implement while toting along 2 younger kids! I found that sometimes I had to resort to reactive parenting i.e. punishment after the fact that wasn't particularly related to the "crime" in question. Sometimes I couldn't even think of a suitable punishment that would mean anything to a small child other than a swift spank.
So yes, I have resorted to spanking on occasion. I still use logical consequences and reasoning whenever I can. My aim with discipline is mainly to TEACH my kids better courses of action for next time. I focus a lot on what is the right thing to do vs what is the wrong thing. But there have been times when my instinct has been to just make a very clear point that what was done was very, very wrong and will NEVER be tolerated. I save the spanks for really, really naughty things that they KNOW are wrong - maybe things that we've dealt with in other ways before that clearly hadn't worked, or outright defiance that is threatening to undermine my authority as a parent. My kids are free to question things, discuss things, negotiate (politely) for change etc. But they are not allowed to rudely defy my directives. And there are times when, for their safety, they will be expected to obey me immediately and without question. They know my "urgent, obey NOW" voice and face.
Spanking doesn't have any value for teaching the right thing to do. It's really only a reaction to the wrong thing. It also loses its effect if used too often or for trivial things. That's why it's not a primary tool that I use. However, I have fallen back on it from time to time, and for that reason I could never denounce it. I'm not sure if I did wrong by my kids the times I used it, but I am the first to admit that I am not and never will be a perfect parent. I am just doing the best I can, like most of us.