I agree that the human has to be seen as a pack leader and have seen with my own eyes (and still do, on a regular basis), when the dog doesn't respect a person.
My dog Keeda heels perfectly as taught when we go for a walk. I can let the leash go and she will continue to walk by my side. She sits at curbs without my asking and performs all of the commands and tricks we learned perfectly for me.
When my mother picks up the leash to take her for a walk, Keeda immediately starts to bolt, tug, pull, and run ahead, dragging my mother with me. She conveniently 'forgets' pretty much all commands she learned and does her own thing. I can see the interaction between them in my mother's body language - my dog is the boss and my mom follows her because "She's just so excited!" or "She's so cute!" or "She's been inside all day, so she's just letting off some steam!"
My dog loves my mom, but doesn't respect her.
I'm not against mild positive punishment, but by this stage I haven't needed to apply any physical force in so long that I can't even remember the last time I had to give her a light spank with the leash. My dog learned, now she knows and listens. This isn't to say that she's perfectly trained - just to say that being the 'leader' works for us in our interaction and I'm happy with where we're at right now.