You're just looking at the headline... it says elsewhere "Kidwell – who is 5ft 6in and weighs 320lbs - allegedly left a bruise on his son's chest after punching him." (Daily Mail).
Punishing your child is one thing, but that punch could've been a lethal blow. So that's probably why he's getting arrested.
Nope, I read the entire article. They are citing the pushups and the leaning against the wall as being part of the charges. And just because the punch left a mark doesn't mean it was a potentially lethal blow. Just because the guy is big and strong doesn't mean he hit him hard enough to cause damage. If he had hauled off with everything he had, he probably would have broken something. He clearly did not. When I spank my kids, it'll leave redness on their behind. What's funny is that, when my wife spanks one of the little kids, they walk away laughing. So I'll say, "Well, how about if I spank you." ... they immediately respond and start begging for mercy

. I'm sorry, but it has to hurt a bit to be any kind of deterrent for bad behavior. I RARELY have to spank my kids anymore. Because they've felt it a few times, I rarely have to do more than threaten it before they immediately comply.