Yes. And the parents who sneak out to smoke aren't just teaching their kids to smoke: they're teaching them to be sneaky. It would be better to smoke openly and say, 'Please don't follow my example. I regret having started.'

Yes!

Admitting to have faults as well, is very important, but especially hard for many, as they think their authority will suffer. Humans are not perfect. Also not parents. Children can handle that.

On the other hand, my parents never snuck around at all, and I was very sneaky as a child/teen.

Yet authority figures set a standard, whether one is able to meet it or not. If they had been sneaky, then I might sneak around sociopathically for the rest of my life, without a twinge of guilt. This could easily mar both my life and others.

That sounds nice but is a superficial and facile simplification that pretends children are not individuals with their own tendencies and influences. There have been good people raised by literal serial killers.

Of course there have been. It also doesn't change the fact that children raised by good parents tend to turn out better. It's a numbers game just like most things in life.

In the long term maybe, but it may take years. If your kid has bullying tendencies now and you let it on just being good example, it may take years of other kids being bullied.

Being a good example for me also means, to stop bullying and in general exploiting of weaker ones.

I also do martial arts with kids. It teaches them how to fight, but more importantly, not needing to fight, especially not weaker ones, to feel superior. If you know you are strong, you don't have to show off. People with low self esteem does that.

Yes, but stopping is not enough. It will just move beyond your back. It is also important to actively teach positive problem solving, deal with underlying reasons for bullying etc.

The same for victim or maybe even more importantly. You have to actively teach the kid behaviors that makes it less likely bullied, in situation when the kid is not bullied right now. Even if you are naturally assertive, the kid may not be and you gotta actively work with it.

Doing things and explaining them if needed, are going together for me.

And didn't I say I do martial arts and it is much more about fighting? If done right, the agressor stops doing so as he don't need it anymore to feel confident and the victim walks upright and does not have written "victim" on their head anymore.

When I need to teach the small kid to hold the toy while the other is trying to take it away, I wont be able to teach that just by explaining while role-modeling. The same when I need to teach a bit older kid to relax and swear back.

Second, no, one intervention is not enough, for neither kid. It takes repeated interventions as behavior goes away and comes back sometimes in different form. It is not just about walking upright either.

These are strong habits in both children when talking about repeated issues. And aggressors motivation are more complicated then just confidence (situation in family that wont go away, parents who encourage aggression etc). In martial club, you need to stop the behavior while in club (not accepted here), in home you deal with it repeatedly and need to change it in situations you don't control at all and know only half of.