As retarded as this is, I'm going to give a legit answer anyway.
The only option for disciplining a dog is voice. Any physical action will cause fear, which will overwrite the "I did something wrong" sensation and completely defeat the purpose. If you've trained it well you can use making it go outside, but if you have to actually physically force it out, again it will defeat the purpose.
So much rage, so few words... Tell your friend he shouldn't have dogs. Or kids. Also animal cruelty has gotten to the point that animal control would probably be willing to respond to someone reporting that statement, or at least look into it.My friend beat the living shit out of the border collie at the time, he loves that dog more than his family, and he treats it like his own son.
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