This is a key question that many commenters do not answer in a useful way. The first observation to make, for me, is that governments have been responsible for arguably the most number of violent deaths in human history - so it is a bit misleading to think that governments protect us from violence. With that in mind, we can perhaps more fairly appraise the validity of real anarchy. I don't think of anarchy as a situation where there needs to be means of protecting against violence, since as soon as violent 'ruling' appears, there is no anarchy. That is not a 'cop out', it is just a fact. So how then to maintain anarchy in a world of would-be rulers?

Whether there is a government or not, the way to non violence requires a balance that itself must start in the heart of all involved. This means that we need to put great emphasis on personal responsibility to understand and learn how to heal, balance and evolve. Every violent act requires a decision to override free will and to act without compassion, so a very strong and reliable focus on bringing awareness to the dynamics involved, which includes an unprecedented collective and new found respect for free will is necessary. The Ubuntu movement out of South Africa is one practical approach which gives good examples of how peace is increased once local agreements are reached to work together in harmony to produce for the needs of the community, it's worth researching.

In cases where there are simply people who are so 'evil' and heartless that no matter what everyone else does, they still try to violently control others, it is not wrong to defend self, but by doing this in an enlightened way, the seeds of future violence are reduced in strength and may eventually cease to be. 'randomly' dropping bombs from robots is pretty much the complete opposite of enlightened defense.