[sparkie]

This is Horseshoe Theory (https://en.wikipedia.org/wiki/Horseshoe_theory). Commentators from both sides will vehemently defend their position and claim it to be nothing like the other side. From the reasonable person's perspective (more towards centre), both extremes are authoritarian, and their similarities are more striking than their differences.

[asabjorn]

It is not a horseshoe, as it is not a continuum. Far-right is pre-modern and far-left is post-modern, and both have a distinctly different view in opposition to the modern enlightenment project. However, the current dominant ideologies on the fringes seem to share some important core tenets and a tendency towards tyranny.

Btw, the article you link seem to argue that there is a historic parallel to this argument. However, post-modernist is a much newer concept and ideology than the historic events listed in it.