1.
The world is full of idiots who ruin the lives of others, both at the micro level of domestic abuse and the macro level of dictatorships, because of this principle.Self-defense isn't the same as aggression, it's an act of self-preservation which is still very much a principle of civilized society. The author of the article failed to make this distinction clear. When you stand up for yourself or a friend you're sending a clear message that says "I'm not going to take this laying down."
"We must begin by acknowledging the hard truth: We will not eradicate violent conflict in our lifetimes. There will be times when nations -- acting individually or in concert -- will find the use of force not only necessary but morally justified."
-Barrack Obama, Nobel Peace Prize Acceptance Speech
2. I do not consider it a valid way to solve problems.
The smart solution to bullying is to make it socially unacceptable.
When you're in a confrontational situation where the other party is about to beat you to a bloody pulp you can't take a time-out to establish a social stigma. Furthermore that wouldn't work. Most bullies are deviant by nature so making something socially unacceptable would just make it more alluring.
3. We live in a civilized society, where intelligence can triumph over brute strength.
But hitting back only works if you're stronger than them.
By the former statement it appears that you exclude violence categorically from the realm of "intelligent things to do." Violence, just like any other human interaction, is a language with its own inflections and subtleties. Without training and practice how do you expect to be fluent or successful in getting your point across?