Anarchy is not chaos. It is the belief that we don't need glorified thieves to rule us for there to be order. We can organize as a community to progress greatly. Look at all the private companies doing research to cure cancer. These people don't need government to progress. Only the will to progress.
Even if true anarchism wants peace and non violence, this will inevitably be a consequence of an anarchist society. Gangs will become a bigger issue. With no deterrent, or punishment, gangs are free to do what they please, whether this be distortion, taking advantage of innocent people trying to live their lives. With gangs growing and more popping up, there will likely be more fighting among them. People will not want to work, progress in technology, and achieve more as a species. There will be no point. This will not promote cultural or technological advances. The concerns I have brought up will halt, or significantly slow down progress.