Danger!
I spend a decent amount of time on the change my view subreddit (assuming you've heard of Reddit) and every once in a while there's a spanking change my view. Most of the time it's "I think spanking is bad, CMV". Occasionally it's the other way around, but I usually find myself commenting on the first comment and the response is almost ALWAYS, "spanking should never be done out of anger, only in extreme circumstances to protect your child from danger." This response is so insanely common, and I'm not going to get into ALL the reasons I'm against it, I'm just going to challenge you to this view:
Adults understand danger. Children do not understand danger. If a child is in a dangerous situation, is it their fault that they are there? Is it their fault you took them to a crowded mall? Is it their fault you left the stove unattended, let them play in the front yard by themselves, took them camping, put the knife down in their reach? No. It's not. I completely understand the frustration, but punishing your child for danger that you put them in is irrational. Protect them from danger, pull them out of those situations, emergencies happen I get it. But it's just a poor justification for physically hurting them. There are ways to teach without violence and when they're too young to understand them, that's when they need you to protect them the most.
That said, there are also neurological reasons why spanking actually can be rather ineffective, but I don't have good solid sources for those claims so I'm not going to post it now, but it just takes a basic understanding of how learning occurs and how the limbic system works. Gabor Mate has some amazing research on it. One day I'll gather all the sources. For now, just keep your kids out of danger and don't blame them for getting into it! I'm guilty of it too, but I don't justify it and I recognize that my reactions were poor and could have been handled better.