Sure they would. And they do. Did you not have siblings??
You're trying to stretch the point to fit. All I'm talking about is the violent approach. "Timeouts", denial of privileges and the like are unrelated here.
When you're down to "it's just the way of things" I think you've run out of argument. Any human of any age --let alone animals-- can understand the concept that "this outside entity is a superior force and will hurt me if I do X". You don't need intellectual development to figure that out. And these equivalencies take root in a young mind long before abstract thought can develop to pick it apart.
Ever see a dog that's been abused? Same thing. Abstract intellect not required.
You could say those things, and they would all be logical. That doesn't mean we cannot draw a line and forbid ourselves to ever eat a plant. What we speak of here is all relative; where we draw the line. The line shifts over time, obviously. Many of us posting here had acts visited on us by our parents that today would land them in jail. But that doesn't mean they were the right thing in their time. Any more than torturing "witches" was the right thing in its time. Again, taking an analogy to extremes, the reason for doing so being that it makes the point more obvious.
I have siblings. I fought with my older brother a ridiculous amount, no matter which of us was bigger or stronger at the time.
My argument was not that 'it's just the way of things' explains why spanking is good, instead I was using that as a description of how I think a young child's mind works regarding authority. I don't think, up until a certain point, that children think overly much about why their parents hold authority over them. I don't think that they are likely to reach the conclusion that might = right, even if it seems the only logical conclusion to an adult. I don't think they necessarily connect the relationship they have with parents or family to their relationships with others. When they do, I don't think it's on a level of might makes right; it's more likely to be something like 'grownups are in charge'. Again, I think you are assigning more adult thinking to small children than is usual.
So, if a child thinks, "Mommy will hurt me if I do X" it doesn't mean that child will think, "That is only bad because mommy will hurt me." or that the child will think, "Hurting someone is how you should get them to do what you want.". If there is abuse, if the only technique ever used to discipline is spanking, if that's the only message ever reinforced, OK. I can see your point. But as an occasional tool? I don't find it likely that a 5 year old makes the connections you do.