It's because leftism will ALWAYS devolve into such authoritarianism that I have always rejected it so hard.

Learning more about how it is physically impossible to work has just cemented my beliefs.

Anyone who is even slightly left-leaning needs to take a long hard think about it, and realize that by definition this is an ideology which will always be against free-association, anti-free speech, anti-free markets, anti-freedom.

Those are literally the defining features of it because it's about control, so that the individual is jammed into the square peg of the 'community'.