Franky said:
The hard part is to find the balance. The real world is always messier. How would you react in the following scenario: you and your girl walking down the street. A guy elbowed your girl. Instead of saying sorry this guy turn his head and stared at your girl. What would you do in this case? You let it go your girl would think you're weak. If you don't this could escalate to a fight. How to be dominant in this case?
Escalate, certainly.
It will rarely end in an actual fight (but be prepared for it to do so) It will more likely be a case of brinksmanship which can go on for quite some time. He would not enjoy a fight either, and he does not know how it will turn out for him, especially if faced with someone who is being confident and aggressive.
Not easy to respond in an assertive way for some guys, for others it seems to come naturally.
Think of some strong,combative people you know and think how they would react (also watch films).
For example you could stare at him scornfully then shake your head and walk away saying "Dick!"
Or say "Hey! Easy Mate!"
Or "Er, Excuse me, what the fuck do you think you're doing?"
If it does come to a fight and you get pasted you will still keep the equilibrium with your girl more than if you did nothing, but don't assume you would get pasted.
Of course if you don't want a potential fight it is perfectly legitimate to avoid one but you have to pay the price for that.
The other problem, which I suffer from, is that such things take me by surprise. I am not able to muster a satisfactory reaction in the couple of seconds available. Very annoying.