Authoritarianism is by definition illiberal and anyone who is authoritarian or supports authoritarianism is not liberal no matter what they claim to be. Centrism is also a meme, anyone who claims to be a centrist is usually just a stan for authoritarians in disguise.
Ok, but now you’re just fiddling with semantics so that your thesis is tautologically true. Sure, if you redefine your terms in a circular way so that authoritarianism means iliberalism and iliberalism means authoritarianism, then obviously its true, but it’s not very meaningful. It also doesn’t really make sense in regards to your original argument that the extremes of left and right are authoritarian, because, by your definition of liberal there is not now and never as been a liberal society. The USA incarcerates a volume of people that dwarfs any of the called ‘authoritarian’ nations, comparable to the Soviet Gulag system at the height of the purges. It also summarily executes people for minor crimes all the time. It frequently overthrows governments and engages in mass killings, including currently committing a genocide. Beyond that, it unilaterally deprives its people of access to the Earths commons using unilateral and lethal force, as well as hording vast quantities of stolen wealth from its rightful owners and using that wealth to oppress them. Other ‘liberal’ countries may not go to the same level, but they all do the same things. They have all been authoritarian and thus not liberal, which would make liberalism an extremist left wing ideology.
The core tenant of liberalism is respect for the autonomy and civil liberties of the individual and consent of the governed to the rules of the government through the machinations of democracy.
That’s all the tenants of leftism, including the ‘extreme’ leftism you call ‘crazy land’. You’re also leaving out the important caveats: autonomy as defined by liberals (So not, for example, autonomy to freely roam the earth and make use of its commons without interruption), civil liberties as defined by liberals (so not, for example, the liberty to make use of the means of production as you like), and consent of the governed as defined by liberals (so not, for example, the ability to ignore the degrees of government that you do not consent to).
The same could be said of the “far left”. They claim to be leftists, and they might have started out as such, but they have stepped out into crazy land and end up supporting things antithetical to the ideologies they claim to subscribe to.
Are you willing to apply this standard to ‘moderate’ liberals; are you willing to extend it to yourself? Will you declare anyone who shows even critical support for existing failed attempts at liberalism (which is all of them, by your definition), as having “stepped out into crazy land and end up supporting things antithetical to the ideologies they claim to subscribe to.”? Do you condemn people who support George Washington the same way as you do people who support Lenin? Do you condemn people who support Lincoln the same way as you do people who support Castro? Do you condemn people who support Churchill the same as people who support Pol Pot? Do you condemn the French Revolution and the American Revolution the same as the Russian and Chinese?
Because if not, I can only conclude that it’s not ‘authoritarianism’ that you consider “crazy land”; it’s just political heterodoxy in general.