Let us begin with this fact: The left always suppresses speech. Since Vladimir Lenin and the Bolshevik Revolution in Russia in 1917, there has been no example of the left in control and not crushing dissent.
That is one of the important differences between liberal and left: Liberalism and liberals believe in free speech. (The present leftist threat to freedom in America, the greatest threat to freedom in American history, is made possible because liberals think they have more to fear from conservatives than from the left. Liberals do not understand that the left regards liberals as their useful idiots.)
The left controls universities. There is little or no dissent allowed at universities.
The left controls nearly every “news” medium. There is little or no dissent in the mainstream media — not in the “news” sections and not in the opinion sections.
The left controls Hollywood. No dissent is allowed in Hollywood.
That is why we have “cancel culture” — the silencing and firing of anyone who publicly dissents from the left, and even “publicly” is no longer necessary. The National Association of Realtors has just announced that if you express dissenting views (on race, especially) in private, you may be fined and lose your membership in the organization — which effectively ends your career as a realtor.
So, we return to the opening question: Why does the left need to crush all dissent? This is a question made all the more stark because there is no parallel on the right: Conservatives do not shut down dissent or debate. The answer, though the left will not acknowledge it, is the left fears dissent. And they do so for good reason. Leftism is essentially a giant balloon filled with nothing but hot air. Therefore, no matter how big the balloon — the Democratic Party, The New York Times, Yale University — all it takes is a mere pin to burst it.
Leftism is venerated by intellectuals. But there is little intellectual substance to leftism. It is a combination of doctrine and emotion. The proof? Those with intellectual depth do not stifle dissent; they welcome it.