No one is disagreeing that governments are the biggest perpetuator of killing in the past 100 years. Government is responsible for far more killing than by non-government actors. Using your interesting logic, one would disagree with the existence of government if one were trying to minimize these deaths. Is this your argument in support of anarchism?

There are complaints that an anarchist society wouldn't be perfect, as though any perfection can be found in any of the well-over 100 governments run on the principle of capitalism plus government authority. Not even the capitalist ideal is respected (freedom to use your private property however you like), since it would cause so many problems in practice.

The history of the supposed poster child of "democracy" w.r.t. its handling of the native peoples inhabiting its territory disagrees with your disagreement.