I do have a story to relate about a kid for whom discipline is...negligible, at best, and when it does occur, its always anger and no explanation. My eldest cousin's first son, Eli, is...I dunno, 6 now, maybe 7. He's been almost entirely raised by his (and my) grandmother, because his mother left him entirely to his father so she could move to Chicago to party til she dies of liver failure, and his father is a consummate lecher with multiple, untreated social diseases and a complete disregard for anyone that isn't him.
Because of this, the son, Eli, has no respect for anyone. He has literally spit on my brother, an act which elicited a very swift, single smack to the dome, a lecture on fucking respect, and being sent to his room and not allowed to come out for more than meals, something with which my uncle (pretty much is only real father figure) agreed. He's been sent home multiple times from school due to disciplinary problems, and he is the archetypal spoiled bratty half-pint who thinks they rule the roost.
When shit gets extreme, like spitting on people or trying to punch them in the nuts (something he also tried on my brother, which got the same reaction above), yeah, smacking them once is, if ya ask me, alright, so long as you also take the time to lecture them on why that shit isn't okay, like my brother did. My bro may be an annoying bastard, at times, but I have almost no doubt in my mind that the difference between him as a father and my cousin would be like night and fucking day. Why? My bro knows how to be authoritative, without being an authoritarian. He's got very clear rules and standards, and knows how to enforce them appropriately. Beating your kid half to death with electrical cable is never fucking appropriate.
This is what happens when you have a completely black-and-white view on discipline: either you're a completely monstrous authoritarian dictator, or you're a pussy. That's not how shit is, and people should fuckin learn that. Give your kids freedom, definitely, but give them structures, standards, and rules that are clear and easy to understand, and are evenly enforced. How some people don't get that is, quite frankly, fucking beyond me.