To have a non-violent culture, one needs consciously cultivate a non-violent culture. One needs to refrain from adoration of violent acts, even if they are committed as acts of self-defense. In a non-violent culture, even wars of self-defense are seen as causes for sorrow and anguish and not as something to be revered.
In a non-violent culture, when these necessary wars are remembered, the acts of violence that were needed to curb the onslaught of the aggressors are not revered and glorified. They are remembered with deep sorrow. They are remembered as moments when good men were forced to commit bad deeds because the situation warranted it.
Even the best of men are sometimes forced to kill fathers, sons and brothers of other men with whom they have no quarrel or enmity, just because the political leaders of these men have lured or outright forced them into that war.
However, there should no reason for jubilation and festivities when we remember their deeds, but time for sorrowful reflection on the evil that war always inevitably is.
No one in his right mind thinks that theft has become extinct from the world just because it has been universally condemned. However, if it would be universally stated that theft is a good thing under certain circumstances, and we cannot ever get rid of theft, and so we just need to live with theft, the willingness of people to steal just could be somewhat heightened.
There are strong interest groups in our societies which want to make sure that violence is condemned only when wrong kind people commit it. The kind of universal condemnation of violence similar to that of theft is just not possible.
Nobody expects that psychopaths would be changed by anything. However, changing our attitude towards violence just can have an effect on the majority of normal people, who just tend to go with the crowd.
The supporters of violence always seem to forget that you need an adversary that wants to use physical violence to have a need for even self-defense. If that person would also think that physical violence is always bad there just would perhaps not be a need for self-defense in the first place.
As long as people propagate the belief that violence is good in some instances, there will more violent tendencies in a society than in a society where all violence is condemned.
The need to fight religious or nationalistic extremists will quite probably never go away. However, if violence would be always treated as evil and disgusting thing that one must use just only if hard pressed to by others and in situations where you simply cannot react with any other means, our world would be a much nicer place to live; there is no doubt about it.
A culture that glorifies and admires violence will always breed violence. This admiration of violence inevitably lowers the threshold for using violence even in situations that would not really warrant it. The evidence for this is everywhere around us.
However, there are extremely strong and vocal forces in our societies, whose interests are best served by maintaining an atmosphere of fear of imminent violence. The need to defend one from thugs (political or otherwise) is a quite different thing than adoration and wholesale acceptance of violence as an accepted means for conducting politics. It is funny how this distinction is so difficult to make for so many people.