I personally am for "smacking" when a child does wrong. Heck it worked for me and I believe I turned out better than if I wasn't disciplined. Though I am not for some cruel way of torture which happenes so often when parents just takes it too far in their actions and cross the line from disciplining to just letting out their anger, that is a no no.
Anyway, the stuff that you mentioned can happen in many forms in other places as well. In the UK I've seen many 8 year olds swearing their heads off in public, throwing tantrums, smashing bottles, just being vandals, terrorising people and not even human like. That kind of attitude disgusts me and the reason for that is that they have no parents to put them straight. It's so easy here to be a parent and have a bunch of kids, throw them into the streets and live off child benefits. Thinking that, I think I am glad that I didn't turn into them because my parents knew better and taught me what is right and wrong (and some smacking at times). Actually, when I ask them to smack me now the funny thing is that they say that I'm too old for it, there goes my sweet memories
Back on topic. I see a father who abandons his "wife" because she wanted to give birth to a child that may kill her as wrong. Even if he disagrees, she has made up her mind and you can't force her not to. Now that is fine that he broke up with her, but he does have some nerve to come back asking for Rin because his wife can't have kids (seriously, I do believe that is the true motive for his actions). I mean, he hasn't helped her and her mother at all, if he did then maybe Aki wouldn't have died of cancer or at least give her a chance with treatments. The guy is an irresponsible mess and I just don't like him. In the long term Reiji will become a problem but for now just kick away the dad.