The point of walking away is to not engage with him and reinforce his irrational behavior. With my ex- the fights weren't about anything; the fight was the fight if that makes sense. Nothing constructive came out of the fight, he wasn't really trying to resolve a conflict. He was just yelling and venting at me. Walking away communicates that you aren't going to engage in that type of interaction.
If he really want to talk and discuss a problem, that's fine, but you don't have to stand there and be his verbal punching bag.