If they are incapable of applying reason, then surely it is fruitless in hitting them?
I would assume you wouldn't hit a 2 month old baby because it is crying?
What about a 14 year old teenager? Are they incapable of applying reason?
At last we are coming to the core of the problem and where we fundamentally differ. I hold the view that small children do have reason(and this is not unsubstanciated btw). What they don't have is the socialisation to deal with their emotions, and thus get frustrated about it.
Watch this video and tell me that children are not yet developed enough to understand or be able to apply reason: