What’s the difference between a fascist and an anarchist who does everything they can to kneecap the only viable left leaning political party in the US?

There’s no practical difference, just window dressing. They both cheer on oppression and pain for those suffering under Republicans.

Left is literally the opposite of authoritarian. You seem to be conflating a whole lot of ideas of terminology here. You sound like an ideological leftist who has been confused by the right's deliberate language-muddying.

Left is egalitarian. That takes many different forms.
Right is authoritarian. That also takes many different forms.

Authoritarianism (or vertical/hierarchical power structure) is THE defining characteristic of the right. "Auth-left" is an oxymoron meant to distract from the fact that wealth and power are one and the same.

Authoritarianism is literally a defining feature of communism. Redefining terms to escape the reality of what ideologies look like when implemented is just dishonest.

So you are not familiar with the concept of communism.

Communism literally - by Marx and Engel's own definition - requires the "withering away of the state". As the creators and originators of the very concept of "communism", can you name one society that has achieved their definition?

Yes, I understand that Marx and Engels did not have realistic political ideals and that every attempt to implement their ideology has diverged from their utopian vision into authoritarianism when reality hits that ideology. That’s the point.