Yes, there are people who are just mean, bullies, or jerks. But there are also those who respond in a moment of jerkiness or they are in a bad place. Or there are also those who respond negatively as a result of our own behaviors, words, or actions.
Withdrawing and walking away and/or reinforcing boundaries are all good tools when dealing with the first group. But when dealing with the other two, is that not a form of denial? flight? freeze? It is always good to let the emotion settle, but when a person is back in a place of relative calm and to go back and revisit can bring about understanding, growth, compassion, empathy, etc.
Human interaction is messy. Relationships are messy. But at some point we have to work through the "messy" and learn to deal better with interaction and relationships. To constantly withdraw will not resolve anything, and I am not necessarily talking about resolution with another person, as there is also personal growth, resolution and acceptance in this process.
Don't get me wrong, this is not about self-blame or being a door mat. It is about an honest appraisal, and looking for ways to grow and become a stronger individual. Assertiveness comes from inner strength, while aggressiveness and passiveness are fed by our own inner insecurities.
There is an old adage that you can learn more from one mistake than one hundred successes. Sometimes you can learn more from one conflict than you can from one hundred positive interactions. Retreat until you are on your feet, but then stand solidly on your own ground and take a look. Kick the assholes to the curb, but don't be afraid to step off your own ground and try to look at it from someone else's perspective. Who knows what a person can see and learn, but there isn't a chance unless you risk it.
JMHO