Non-violence or pacifism?

Listening to Nelson Mandela's autobiography 'Long Walk to Freedom' (audio books are my most recent pleasure, especially since purchasing a 'Parrot' in-car speaker system to I can actually hear them properly!), my ears pricked up when he mentioned his opinion on the difference between non-violence and pacifism.  It's not something I'd ever thought about before, but since I claim to work with horses in a 'non-violent' way, I looked it up.  As I heard it, Mandela seemed to be saying that non-violence meant being opposed to violence in any situation, whereas pacifism meant being opposed to violence but violence may be used in self defence.

Wikipedia says, amongst other things "Nonviolence is the personal practice of being harmless to self and others under every condition"  and "Pacifism is opposition to war and violence... and opposition to violence under any circumstance, even defence of self and others.... Some pacifists follow principles of nonviolence, believing that nonviolent action is morally superior and/or most effective. Some however, support physical violence for emergency defence of self or others."

It seems to me there's a lot of confusion - as usual, words are used simply as labels, and the intended meaning may well vary from person to person.  As far as working with horses goes, I would certainly say that I aim to avoid using violence of any form (but there again, what is your definition of violence?!), and that in this matter I am acting as a pacifist.  However, I believe that the safety of the human (and often the horse at the same time) is paramount, and if I or others were in danger, I believe I would do whatever I felt necessary to alleviate the danger.  My priority is always to avoid dangerous situations, which is where I feel that knowledge and experience play an essential role, but ultimately my feeling is that if the human is injured or worse, then who will look after the horse?!