I have mixed views on this. I understand all the 'teaching them violence stuff' but ... I DID smack both my sons when they were young. I didn't beat them up or anything but I don't see the problem with a short sharp lesson (smack) at the time of the incident (whatever it is) if they don't stop doing whatever it is when told. It's all very well saying you should reason with them, but does a 2-year-old want a long philosophical lecture on why they should't do what they insist on doing? I had a friend who'd have gouged her own eyes out rather than lift a finger to her child. So - she's refusing to let him have his own way about something, and what does this 2-year-old do? He gives her a right hard kick. Where did he learn the violence?
People who ALWAYS try the reasoning approach don't always succeed and can end up with some really obnoxious little turds as offspring.
I think what I'm saying is that it has to be a combination of both methods. And the child has to realise that at this point in their life, the adult is in control.