Agreed, I am completely uncomfortable with that. Once you indicate to someone that you do not trust them, why should they trust you?

The sad thing is that he is actually sounding reasonable to himself (and to others I am sure), because he is advocating against an even worse behaviour (like yelling at people).

Also, how to deal with children is not a good framework for how to deal with adults

Agreed, but it's not like his childrearing advice is that great either. Yeah, you can threaten to take the lego away from two fighting children, but it's better to teach them the skills to negotiate possession.