I too classify all my physics problems as 'spherical cows in a vacuum', but unless you've ignored Twitter your entire life you should realize powerful forces of propaganda exist that ensure that this will never exist. Threats exist in the form of ruthless humans that will ally with the corruptible and greedy to consolidate power to the point of acting with wonton violence. These people use ideas of nationalism and shared identity (cooperation) along with propaganda that militarizes the group against common enemies, generally being other groups that have resources they can take.

In general having a 'stable' society with wealth can be an inoculation against this human behavior of falling for propaganda, but again, it requires stability against the environment, against disease, against economic swings, against competing ideas. Anarchist societies just seem to handwave these issues away.