Your case is terrible, because that’s not how science is done.

In science, we control for variables, anarchist societies can’t control for the variable of very powerful people destroying them.

Furthermore, their destruction was ENTIRELY external, their internal politics flourished such that george orwell wrote an entire book praising it https://en.wikipedia.org/wiki/Homage_to_Catalonia

Now, if you can demonstrate that the variables were controlled for in any of the anarchist societies that existed, and that they failed purely by their own merit, you’d have a point!