Can non-violence become violence?

Buddhism, like Jainism and Hinduism, emphasise non-violence (Sanskrit ahiṃsā) as a fundamental tenant of the Dharma. Non-violence is, of course, a great thing in itself as we should all try our best to avoid harming others - yet can it be used to extremes, and become a form of violence in itself?

The most obvious example is:

Someone breaks into your house and attempts to kill you for whatever reason; maybe that they didn't expect anyone to catch them in the act, but nevertheless, they're coming at you with a knife. Your spouse and children are asleep upstairs, and you don't think if they kill you, they will just walk out but they will go for them. You have two choices: fight for your survival, even if meant killing the person, or die and risk your family dying, and this could happen again to another person.

Which is more violent?

My opinion, not fighting is more violent than fighting when it allows injustice and cruelty to continue. Sometimes fighting is necessary--in self defence, of course. I'm not suggesting you go out there and beat the shit out of some elderly person, with a cry of "Not fighting is more violent than fighting!"--that would be violent.

Most of us agree that we should do what we can to defend ourselves and our families if we have an attacker coming after us, yet there are some people who think that an "enlightened person" would not do that, that an enlightened person would not use force to defend themselves or their loved ones.

Of course, not everything is as threatening as this.

Yet is it still violence to walk past as an old woman gets attacked by someone for her money? What about violence to yourself, such as practising extreme forms of asceticism like keeping one's arms in the air so you end up becoming dependent on others to do your basic necessities, or starving yourself for months at a time? What about swerving out of the way for butterflies whilst driving, consequently endangering others? Are these violence to oneself?

I think they are all forms of violence. Violence does not always have to equal you hitting, stabbing, or punching something. This is direct violence, but I feel as though there is another level to violence--indirect violence: harming by not doing. It is not as bad as deliberately going out of one's way to harm someone, but I feel that there would most likely be negative consequences for not stopping what one can.

Non-violence, in my opinion is to not harm the innocent but also to preserve peace even if it means kicking the violent person's ass, of course, avoiding conscious excess: if you can stop the guy by shouting, then you don't need to hit him. If during a struggle you kill the attacker, is that wrong? I do not believe that to be the case; what would be wrong is not attempting to stop the violence.

The violent should not be protected by the rule of non-violence.
It was, after all, their choice to commit the crime.